<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019e2c54-e5ef-7eb7-9839-6eac2f792844,g:384dd3bf-3840-4b5a-9b45-cc3baa1bfa97-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://www.unitedcontinentalholdings.com/role/CoverPage" xlink:type="simple" xlink:href="ual-20260630.xsd#CoverPage"/>
  <link:definitionLink xlink:role="http://www.unitedcontinentalholdings.com/role/CoverPage" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityInformationLineItems_019e2c54-e781-7cef-bb32-9b96e5a3ab62" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitiesTable_019e2c54-e781-7ae9-b067-baf041b4abf2" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntitiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_EntityInformationLineItems_019e2c54-e781-7cef-bb32-9b96e5a3ab62" xlink:to="loc_dei_EntitiesTable_019e2c54-e781-7ae9-b067-baf041b4abf2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019e2c54-e781-799b-a40c-f4212a136af7" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_EntitiesTable_019e2c54-e781-7ae9-b067-baf041b4abf2" xlink:to="loc_dei_LegalEntityAxis_019e2c54-e781-799b-a40c-f4212a136af7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019e2c54-e781-799b-a40c-f4212a136af7_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019e2c54-e781-799b-a40c-f4212a136af7" xlink:to="loc_dei_EntityDomain_019e2c54-e781-799b-a40c-f4212a136af7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019e2c54-e781-74a7-b159-8fdd7ef12947" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019e2c54-e781-799b-a40c-f4212a136af7" xlink:to="loc_dei_EntityDomain_019e2c54-e781-74a7-b159-8fdd7ef12947" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_UnitedAirLinesIncMember_019e2c54-e781-77b9-8f78-a129f4641a92" xlink:href="ual-20260630.xsd#ual_UnitedAirLinesIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019e2c54-e781-74a7-b159-8fdd7ef12947" xlink:to="loc_ual_UnitedAirLinesIncMember_019e2c54-e781-77b9-8f78-a129f4641a92" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019e2c54-e781-757a-8149-d7c2e41327d2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_EntitiesTable_019e2c54-e781-7ae9-b067-baf041b4abf2" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019e2c54-e781-757a-8149-d7c2e41327d2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019e2c54-e781-757a-8149-d7c2e41327d2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019e2c54-e781-757a-8149-d7c2e41327d2" xlink:to="loc_us-gaap_ClassOfStockDomain_019e2c54-e781-757a-8149-d7c2e41327d2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019e2c54-e781-7a56-b1be-73209572911e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019e2c54-e781-757a-8149-d7c2e41327d2" xlink:to="loc_us-gaap_ClassOfStockDomain_019e2c54-e781-7a56-b1be-73209572911e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_019e2c54-e781-7360-a5d5-0f5c219f5daa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019e2c54-e781-7a56-b1be-73209572911e" xlink:to="loc_us-gaap_CommonStockMember_019e2c54-e781-7360-a5d5-0f5c219f5daa" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WarrantMember_019e2c54-e781-7e1d-9ead-94a96b175ccd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_WarrantMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019e2c54-e781-7a56-b1be-73209572911e" xlink:to="loc_us-gaap_WarrantMember_019e2c54-e781-7e1d-9ead-94a96b175ccd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_019e2c54-e781-7fe9-a5aa-ef004bdf23a8" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentType"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e2c54-e781-7cef-bb32-9b96e5a3ab62" xlink:to="loc_dei_DocumentType_019e2c54-e781-7fe9-a5aa-ef004bdf23a8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentQuarterlyReport_019e2c54-e781-7333-8294-cbb28e22d223" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentQuarterlyReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e2c54-e781-7cef-bb32-9b96e5a3ab62" xlink:to="loc_dei_DocumentQuarterlyReport_019e2c54-e781-7333-8294-cbb28e22d223" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_019e2c54-e781-764c-bbd7-eeb1d92a7a47" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentPeriodEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e2c54-e781-7cef-bb32-9b96e5a3ab62" xlink:to="loc_dei_DocumentPeriodEndDate_019e2c54-e781-764c-bbd7-eeb1d92a7a47" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentTransitionReport_019e2c54-e781-72e1-b100-49bf7bbeeaeb" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentTransitionReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e2c54-e781-7cef-bb32-9b96e5a3ab62" xlink:to="loc_dei_DocumentTransitionReport_019e2c54-e781-72e1-b100-49bf7bbeeaeb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_019e2c54-e781-7ab9-88f6-f0b14ac72b93" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityFileNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e2c54-e781-7cef-bb32-9b96e5a3ab62" xlink:to="loc_dei_EntityFileNumber_019e2c54-e781-7ab9-88f6-f0b14ac72b93" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_019e2c54-e781-7d40-ad33-dda447c30403" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityRegistrantName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e2c54-e781-7cef-bb32-9b96e5a3ab62" xlink:to="loc_dei_EntityRegistrantName_019e2c54-e781-7d40-ad33-dda447c30403" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_019e2c54-e781-7648-b94c-e5de8a402489" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressAddressLine1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e2c54-e781-7cef-bb32-9b96e5a3ab62" xlink:to="loc_dei_EntityAddressAddressLine1_019e2c54-e781-7648-b94c-e5de8a402489" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_019e2c54-e781-70e2-8e01-dbd05474b2ca" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressCityOrTown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e2c54-e781-7cef-bb32-9b96e5a3ab62" xlink:to="loc_dei_EntityAddressCityOrTown_019e2c54-e781-70e2-8e01-dbd05474b2ca" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_019e2c54-e781-7d44-b68c-fa19708a8537" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressStateOrProvince"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e2c54-e781-7cef-bb32-9b96e5a3ab62" xlink:to="loc_dei_EntityAddressStateOrProvince_019e2c54-e781-7d44-b68c-fa19708a8537" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_019e2c54-e781-73e8-9794-1680b7294873" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressPostalZipCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e2c54-e781-7cef-bb32-9b96e5a3ab62" xlink:to="loc_dei_EntityAddressPostalZipCode_019e2c54-e781-73e8-9794-1680b7294873" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_019e2c54-e781-7f9d-9623-6c9663829db1" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_CityAreaCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e2c54-e781-7cef-bb32-9b96e5a3ab62" xlink:to="loc_dei_CityAreaCode_019e2c54-e781-7f9d-9623-6c9663829db1" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_019e2c54-e781-7867-b969-5abb4ceabe4f" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LocalPhoneNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e2c54-e781-7cef-bb32-9b96e5a3ab62" xlink:to="loc_dei_LocalPhoneNumber_019e2c54-e781-7867-b969-5abb4ceabe4f" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_019e2c54-e781-7321-be09-cb0d0b602dbf" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityIncorporationStateCountryCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e2c54-e781-7cef-bb32-9b96e5a3ab62" xlink:to="loc_dei_EntityIncorporationStateCountryCode_019e2c54-e781-7321-be09-cb0d0b602dbf" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_019e2c54-e781-7c18-85e4-f0e148eb2661" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e2c54-e781-7cef-bb32-9b96e5a3ab62" xlink:to="loc_dei_EntityTaxIdentificationNumber_019e2c54-e781-7c18-85e4-f0e148eb2661" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_019e2c54-e781-71a8-b1fa-8b1ee794359e" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_Security12bTitle"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e2c54-e781-7cef-bb32-9b96e5a3ab62" xlink:to="loc_dei_Security12bTitle_019e2c54-e781-71a8-b1fa-8b1ee794359e" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_019e2c54-e781-785c-a04e-457adb83c23a" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_TradingSymbol"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e2c54-e781-7cef-bb32-9b96e5a3ab62" xlink:to="loc_dei_TradingSymbol_019e2c54-e781-785c-a04e-457adb83c23a" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_019e2c54-e781-7a1e-ba50-ec405b84bb34" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_SecurityExchangeName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e2c54-e781-7cef-bb32-9b96e5a3ab62" xlink:to="loc_dei_SecurityExchangeName_019e2c54-e781-7a1e-ba50-ec405b84bb34" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCurrentReportingStatus_019e2c54-e781-7a9c-87ac-8acdbb9ca736" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityCurrentReportingStatus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e2c54-e781-7cef-bb32-9b96e5a3ab62" xlink:to="loc_dei_EntityCurrentReportingStatus_019e2c54-e781-7a9c-87ac-8acdbb9ca736" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityInteractiveDataCurrent_019e2c54-e781-7fae-aac1-3ce980746bda" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityInteractiveDataCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e2c54-e781-7cef-bb32-9b96e5a3ab62" xlink:to="loc_dei_EntityInteractiveDataCurrent_019e2c54-e781-7fae-aac1-3ce980746bda" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFilerCategory_019e2c54-e781-70be-94c3-add32eee21c9" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityFilerCategory"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e2c54-e781-7cef-bb32-9b96e5a3ab62" xlink:to="loc_dei_EntityFilerCategory_019e2c54-e781-70be-94c3-add32eee21c9" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitySmallBusiness_019e2c54-e781-737b-8207-6db7592728ea" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntitySmallBusiness"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e2c54-e781-7cef-bb32-9b96e5a3ab62" xlink:to="loc_dei_EntitySmallBusiness_019e2c54-e781-737b-8207-6db7592728ea" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_019e2c54-e781-7800-8e74-db967ed949a4" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityEmergingGrowthCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e2c54-e781-7cef-bb32-9b96e5a3ab62" xlink:to="loc_dei_EntityEmergingGrowthCompany_019e2c54-e781-7800-8e74-db967ed949a4" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityShellCompany_019e2c54-e781-7803-b2ee-ca0338391c34" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityShellCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e2c54-e781-7cef-bb32-9b96e5a3ab62" xlink:to="loc_dei_EntityShellCompany_019e2c54-e781-7803-b2ee-ca0338391c34" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCommonStockSharesOutstanding_019e2c54-e781-75f3-a12a-ed1777547768" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityCommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e2c54-e781-7cef-bb32-9b96e5a3ab62" xlink:to="loc_dei_EntityCommonStockSharesOutstanding_019e2c54-e781-75f3-a12a-ed1777547768" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalPeriodFocus_019e2c54-e781-7441-a1c5-09c141cb7287" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentFiscalPeriodFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e2c54-e781-7cef-bb32-9b96e5a3ab62" xlink:to="loc_dei_DocumentFiscalPeriodFocus_019e2c54-e781-7441-a1c5-09c141cb7287" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_019e2c54-e781-784a-9aca-48ff999a5fce" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_AmendmentFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e2c54-e781-7cef-bb32-9b96e5a3ab62" xlink:to="loc_dei_AmendmentFlag_019e2c54-e781-784a-9aca-48ff999a5fce" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalYearFocus_019e2c54-e781-7a43-aa03-46feda04cc56" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentFiscalYearFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e2c54-e781-7cef-bb32-9b96e5a3ab62" xlink:to="loc_dei_DocumentFiscalYearFocus_019e2c54-e781-7a43-aa03-46feda04cc56" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CurrentFiscalYearEndDate_019e2c54-e781-7021-a2d6-8eecbebffd70" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_CurrentFiscalYearEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e2c54-e781-7cef-bb32-9b96e5a3ab62" xlink:to="loc_dei_CurrentFiscalYearEndDate_019e2c54-e781-7021-a2d6-8eecbebffd70" xlink:type="arc" order="27"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_019e2c54-e781-7f27-9ad2-2447c0a3136b" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityCentralIndexKey"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e2c54-e781-7cef-bb32-9b96e5a3ab62" xlink:to="loc_dei_EntityCentralIndexKey_019e2c54-e781-7f27-9ad2-2447c0a3136b" xlink:type="arc" order="28"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.unitedcontinentalholdings.com/role/STATEMENTSOFCONSOLIDATEDOPERATIONSUNAUDITEDUAH" xlink:type="simple" xlink:href="ual-20260630.xsd#STATEMENTSOFCONSOLIDATEDOPERATIONSUNAUDITEDUAH"/>
  <link:definitionLink xlink:role="http://www.unitedcontinentalholdings.com/role/STATEMENTSOFCONSOLIDATEDOPERATIONSUNAUDITEDUAH" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019e2c54-e781-75fb-8e15-674f156a4e47" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019e2c54-e781-7823-b562-4107c74971ba" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e781-75fb-8e15-674f156a4e47" xlink:to="loc_us-gaap_StatementTable_019e2c54-e781-7823-b562-4107c74971ba" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019e2c54-e781-7606-84c5-acb3295d9a1a" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019e2c54-e781-7823-b562-4107c74971ba" xlink:to="loc_srt_ProductOrServiceAxis_019e2c54-e781-7606-84c5-acb3295d9a1a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019e2c54-e781-7606-84c5-acb3295d9a1a_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019e2c54-e781-7606-84c5-acb3295d9a1a" xlink:to="loc_srt_ProductsAndServicesDomain_019e2c54-e781-7606-84c5-acb3295d9a1a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019e2c54-e781-7467-86ec-eb8367b2aeda" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019e2c54-e781-7606-84c5-acb3295d9a1a" xlink:to="loc_srt_ProductsAndServicesDomain_019e2c54-e781-7467-86ec-eb8367b2aeda" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PassengerMember_019e2c54-e781-73a9-94dc-85c08b16c4cd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PassengerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019e2c54-e781-7467-86ec-eb8367b2aeda" xlink:to="loc_us-gaap_PassengerMember_019e2c54-e781-73a9-94dc-85c08b16c4cd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CargoAndFreightMember_019e2c54-e781-78fc-8876-1e900be2ae22" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CargoAndFreightMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019e2c54-e781-7467-86ec-eb8367b2aeda" xlink:to="loc_us-gaap_CargoAndFreightMember_019e2c54-e781-78fc-8876-1e900be2ae22" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductAndServiceOtherMember_019e2c54-e781-7051-8042-8b0f6d0e9c4d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProductAndServiceOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019e2c54-e781-7467-86ec-eb8367b2aeda" xlink:to="loc_us-gaap_ProductAndServiceOtherMember_019e2c54-e781-7051-8042-8b0f6d0e9c4d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesAbstract_019e2c54-e781-7835-8039-f094fe1a85d6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenuesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e781-75fb-8e15-674f156a4e47" xlink:to="loc_us-gaap_RevenuesAbstract_019e2c54-e781-7835-8039-f094fe1a85d6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019e2c54-e781-75f4-a3e3-61944d486996" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_019e2c54-e781-7835-8039-f094fe1a85d6" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019e2c54-e781-75f4-a3e3-61944d486996" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpensesAbstract_019e2c54-e781-7cfe-bf66-c715a162d6dc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CostsAndExpensesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e781-75fb-8e15-674f156a4e47" xlink:to="loc_us-gaap_CostsAndExpensesAbstract_019e2c54-e781-7cfe-bf66-c715a162d6dc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LaborAndRelatedExpense_019e2c54-e781-71ca-b310-bfea95b7d5fb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LaborAndRelatedExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019e2c54-e781-7cfe-bf66-c715a162d6dc" xlink:to="loc_us-gaap_LaborAndRelatedExpense_019e2c54-e781-71ca-b310-bfea95b7d5fb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FuelCosts_019e2c54-e781-793f-bd6a-e58504268ac6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FuelCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019e2c54-e781-7cfe-bf66-c715a162d6dc" xlink:to="loc_us-gaap_FuelCosts_019e2c54-e781-793f-bd6a-e58504268ac6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LandingFeesAndOtherRentals_019e2c54-e781-7b02-94c4-4dd8519dc72a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LandingFeesAndOtherRentals"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019e2c54-e781-7cfe-bf66-c715a162d6dc" xlink:to="loc_us-gaap_LandingFeesAndOtherRentals_019e2c54-e781-7b02-94c4-4dd8519dc72a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AircraftMaintenanceMaterialsAndRepairs_019e2c54-e781-7812-af45-1a386c3713d4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AircraftMaintenanceMaterialsAndRepairs"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019e2c54-e781-7cfe-bf66-c715a162d6dc" xlink:to="loc_us-gaap_AircraftMaintenanceMaterialsAndRepairs_019e2c54-e781-7812-af45-1a386c3713d4" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_019e2c54-e781-730b-ac00-8c8b1c5f012d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DepreciationDepletionAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019e2c54-e781-7cfe-bf66-c715a162d6dc" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_019e2c54-e781-730b-ac00-8c8b1c5f012d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AirlineCapacityPurchaseArrangements_019e2c54-e781-7f60-a3a9-f45cb000e09c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AirlineCapacityPurchaseArrangements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019e2c54-e781-7cfe-bf66-c715a162d6dc" xlink:to="loc_us-gaap_AirlineCapacityPurchaseArrangements_019e2c54-e781-7f60-a3a9-f45cb000e09c" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingExpense_019e2c54-e781-7c6b-9012-314ee61ee81e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SellingExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019e2c54-e781-7cfe-bf66-c715a162d6dc" xlink:to="loc_us-gaap_SellingExpense_019e2c54-e781-7c6b-9012-314ee61ee81e" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AircraftRental_019e2c54-e781-7230-aaf1-90d059f85c91" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AircraftRental"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019e2c54-e781-7cfe-bf66-c715a162d6dc" xlink:to="loc_us-gaap_AircraftRental_019e2c54-e781-7230-aaf1-90d059f85c91" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringSettlementAndImpairmentProvisions_019e2c54-e781-7ea9-a06b-51146792b035" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringSettlementAndImpairmentProvisions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019e2c54-e781-7cfe-bf66-c715a162d6dc" xlink:to="loc_us-gaap_RestructuringSettlementAndImpairmentProvisions_019e2c54-e781-7ea9-a06b-51146792b035" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCostAndExpenseOperating_019e2c54-e781-7395-af31-ae66895a6d93" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherCostAndExpenseOperating"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019e2c54-e781-7cfe-bf66-c715a162d6dc" xlink:to="loc_us-gaap_OtherCostAndExpenseOperating_019e2c54-e781-7395-af31-ae66895a6d93" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpenses_019e2c54-e781-7c7a-b741-d732d3ba9ca3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CostsAndExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019e2c54-e781-7cfe-bf66-c715a162d6dc" xlink:to="loc_us-gaap_CostsAndExpenses_019e2c54-e781-7c7a-b741-d732d3ba9ca3" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_019e2c54-e781-77bb-bd53-466faf286052" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e781-75fb-8e15-674f156a4e47" xlink:to="loc_us-gaap_OperatingIncomeLoss_019e2c54-e781-77bb-bd53-466faf286052" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonoperatingIncomeExpenseAbstract_019e2c54-e781-71ba-9240-ee2abb4df79c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NonoperatingIncomeExpenseAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e781-75fb-8e15-674f156a4e47" xlink:to="loc_us-gaap_NonoperatingIncomeExpenseAbstract_019e2c54-e781-71ba-9240-ee2abb4df79c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseNonoperating_019e2c54-e781-7e87-aa6f-07f72dcbf29d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestExpenseNonoperating"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_019e2c54-e781-71ba-9240-ee2abb4df79c" xlink:to="loc_us-gaap_InterestExpenseNonoperating_019e2c54-e781-7e87-aa6f-07f72dcbf29d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentIncomeInterest_019e2c54-e781-733e-950f-5b117f7f7add" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentIncomeInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_019e2c54-e781-71ba-9240-ee2abb4df79c" xlink:to="loc_us-gaap_InvestmentIncomeInterest_019e2c54-e781-733e-950f-5b117f7f7add" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestCostsCapitalizedAdjustment_019e2c54-e781-7fbd-924f-108192225d88" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestCostsCapitalizedAdjustment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_019e2c54-e781-71ba-9240-ee2abb4df79c" xlink:to="loc_us-gaap_InterestCostsCapitalizedAdjustment_019e2c54-e781-7fbd-924f-108192225d88" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrealizedGainLossOnInvestments_019e2c54-e781-71b4-af04-5f12ddb28d38" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnrealizedGainLossOnInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_019e2c54-e781-71ba-9240-ee2abb4df79c" xlink:to="loc_us-gaap_UnrealizedGainLossOnInvestments_019e2c54-e781-71b4-af04-5f12ddb28d38" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_019e2c54-e781-7309-8bdb-656bcf781280" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_019e2c54-e781-71ba-9240-ee2abb4df79c" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_019e2c54-e781-7309-8bdb-656bcf781280" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonoperatingIncomeExpense_019e2c54-e781-7137-8593-b20354f526e7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_019e2c54-e781-71ba-9240-ee2abb4df79c" xlink:to="loc_us-gaap_NonoperatingIncomeExpense_019e2c54-e781-7137-8593-b20354f526e7" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019e2c54-e782-7cf3-b710-c1ac6171ca9f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e781-75fb-8e15-674f156a4e47" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019e2c54-e782-7cf3-b710-c1ac6171ca9f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_019e2c54-e782-7fab-9a8b-be7f81172e92" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e781-75fb-8e15-674f156a4e47" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_019e2c54-e782-7fab-9a8b-be7f81172e92" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019e2c54-e782-70d7-8633-67fd327ff637" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e781-75fb-8e15-674f156a4e47" xlink:to="loc_us-gaap_NetIncomeLoss_019e2c54-e782-70d7-8633-67fd327ff637" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_019e2c54-e782-7ada-88f4-38269b8dd5ea" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e781-75fb-8e15-674f156a4e47" xlink:to="loc_us-gaap_EarningsPerShareBasic_019e2c54-e782-7ada-88f4-38269b8dd5ea" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_019e2c54-e782-7127-a178-aaa6f4ec8770" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e781-75fb-8e15-674f156a4e47" xlink:to="loc_us-gaap_EarningsPerShareDiluted_019e2c54-e782-7127-a178-aaa6f4ec8770" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.unitedcontinentalholdings.com/role/STATEMENTSOFCONSOLIDATEDSTOCKHOLDERSEQUITYUNAUDITEDUAH" xlink:type="simple" xlink:href="ual-20260630.xsd#STATEMENTSOFCONSOLIDATEDSTOCKHOLDERSEQUITYUNAUDITEDUAH"/>
  <link:definitionLink xlink:role="http://www.unitedcontinentalholdings.com/role/STATEMENTSOFCONSOLIDATEDSTOCKHOLDERSEQUITYUNAUDITEDUAH" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019e2c54-e782-7960-b215-0fad02c86178" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019e2c54-e782-740f-a209-7ca5f13302ec" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e782-7960-b215-0fad02c86178" xlink:to="loc_us-gaap_StatementTable_019e2c54-e782-740f-a209-7ca5f13302ec" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019e2c54-e782-73ad-9812-925f47c244ef" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019e2c54-e782-740f-a209-7ca5f13302ec" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019e2c54-e782-73ad-9812-925f47c244ef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019e2c54-e782-73ad-9812-925f47c244ef_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019e2c54-e782-73ad-9812-925f47c244ef" xlink:to="loc_us-gaap_EquityComponentDomain_019e2c54-e782-73ad-9812-925f47c244ef_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019e2c54-e782-7451-bae6-440e21a4deb7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019e2c54-e782-73ad-9812-925f47c244ef" xlink:to="loc_us-gaap_EquityComponentDomain_019e2c54-e782-7451-bae6-440e21a4deb7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_019e2c54-e782-7995-8fd6-b1b4ab2b6b48" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019e2c54-e782-7451-bae6-440e21a4deb7" xlink:to="loc_us-gaap_CommonStockMember_019e2c54-e782-7995-8fd6-b1b4ab2b6b48" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_019e2c54-e782-7cb5-9662-56c452b0b3c2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019e2c54-e782-7451-bae6-440e21a4deb7" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_019e2c54-e782-7cb5-9662-56c452b0b3c2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonMember_019e2c54-e782-74a9-8cfa-0d682f7edd68" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockCommonMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019e2c54-e782-7451-bae6-440e21a4deb7" xlink:to="loc_us-gaap_TreasuryStockCommonMember_019e2c54-e782-74a9-8cfa-0d682f7edd68" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_019e2c54-e782-7724-b27d-c03ea53c0881" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019e2c54-e782-7451-bae6-440e21a4deb7" xlink:to="loc_us-gaap_RetainedEarningsMember_019e2c54-e782-7724-b27d-c03ea53c0881" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019e2c54-e782-7d17-8dbe-6e7363ca381b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019e2c54-e782-7451-bae6-440e21a4deb7" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019e2c54-e782-7d17-8dbe-6e7363ca381b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e2c54-e782-7bbc-a72f-378683332398" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e782-7960-b215-0fad02c86178" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e2c54-e782-7bbc-a72f-378683332398" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_019e2c54-e782-79c1-8732-5c798ee32c7a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e2c54-e782-7bbc-a72f-378683332398" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_019e2c54-e782-79c1-8732-5c798ee32c7a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019e2c54-e782-7d5c-bf16-cbd417712834" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e2c54-e782-7bbc-a72f-378683332398" xlink:to="loc_us-gaap_StockholdersEquity_019e2c54-e782-7d5c-bf16-cbd417712834" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019e2c54-e782-71f7-941d-012b90dd2bb9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e2c54-e782-7bbc-a72f-378683332398" xlink:to="loc_us-gaap_NetIncomeLoss_019e2c54-e782-71f7-941d-012b90dd2bb9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019e2c54-e782-7faf-9eae-4775ee12fc18" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e2c54-e782-7bbc-a72f-378683332398" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019e2c54-e782-7faf-9eae-4775ee12fc18" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_019e2c54-e782-7293-9c65-b57763003874" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e2c54-e782-7bbc-a72f-378683332398" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_019e2c54-e782-7293-9c65-b57763003874" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockSharesAcquired_019e2c54-e782-7d43-ac66-782a3555cc8c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockSharesAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e2c54-e782-7bbc-a72f-378683332398" xlink:to="loc_us-gaap_TreasuryStockSharesAcquired_019e2c54-e782-7d43-ac66-782a3555cc8c" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_019e2c54-e782-7156-a6d9-3fc9d1918f85" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockValueAcquiredCostMethod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e2c54-e782-7bbc-a72f-378683332398" xlink:to="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_019e2c54-e782-7156-a6d9-3fc9d1918f85" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_StockIssuedDuringPeriodSharesNetShareSettlementFromWarrantsExercised_019e2c54-e782-7acc-b9a9-1b3f02c5b8c6" xlink:href="ual-20260630.xsd#ual_StockIssuedDuringPeriodSharesNetShareSettlementFromWarrantsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e2c54-e782-7bbc-a72f-378683332398" xlink:to="loc_ual_StockIssuedDuringPeriodSharesNetShareSettlementFromWarrantsExercised_019e2c54-e782-7acc-b9a9-1b3f02c5b8c6" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_StockIssuedDuringPeriodValueNetShareSettlementFromWarrantsExercised_019e2c54-e782-747e-a9e8-eb36bd46920a" xlink:href="ual-20260630.xsd#ual_StockIssuedDuringPeriodValueNetShareSettlementFromWarrantsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e2c54-e782-7bbc-a72f-378683332398" xlink:to="loc_ual_StockIssuedDuringPeriodValueNetShareSettlementFromWarrantsExercised_019e2c54-e782-747e-a9e8-eb36bd46920a" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_019e2c54-e782-7aab-9f61-95e673834e03" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e2c54-e782-7bbc-a72f-378683332398" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_019e2c54-e782-7aab-9f61-95e673834e03" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_SharesIssuedValueShareBasedPaymentArrangementAfterForfeitureNetOfAdjustmentsToAdditionalPaidInCapital_019e2c54-e782-7404-86dd-3728203f814e" xlink:href="ual-20260630.xsd#ual_SharesIssuedValueShareBasedPaymentArrangementAfterForfeitureNetOfAdjustmentsToAdditionalPaidInCapital"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e2c54-e782-7bbc-a72f-378683332398" xlink:to="loc_ual_SharesIssuedValueShareBasedPaymentArrangementAfterForfeitureNetOfAdjustmentsToAdditionalPaidInCapital_019e2c54-e782-7404-86dd-3728203f814e" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_019e2c54-e782-74f2-a3d2-1e589c6acf8e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019e2c54-e782-790e-ac8e-53dc92ffc1f9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquity"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.unitedcontinentalholdings.com/role/STATEMENTSOFCONSOLIDATEDOPERATIONSUNAUDITEDUA" xlink:type="simple" xlink:href="ual-20260630.xsd#STATEMENTSOFCONSOLIDATEDOPERATIONSUNAUDITEDUA"/>
  <link:definitionLink xlink:role="http://www.unitedcontinentalholdings.com/role/STATEMENTSOFCONSOLIDATEDOPERATIONSUNAUDITEDUA" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019e2c54-e782-71b0-84b2-e3347dc01272" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019e2c54-e782-7111-a958-27ec6b3557a6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e782-71b0-84b2-e3347dc01272" xlink:to="loc_us-gaap_StatementTable_019e2c54-e782-7111-a958-27ec6b3557a6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019e2c54-e782-71bf-8868-2374461d2fd8" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019e2c54-e782-7111-a958-27ec6b3557a6" xlink:to="loc_dei_LegalEntityAxis_019e2c54-e782-71bf-8868-2374461d2fd8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019e2c54-e782-71bf-8868-2374461d2fd8_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019e2c54-e782-71bf-8868-2374461d2fd8" xlink:to="loc_dei_EntityDomain_019e2c54-e782-71bf-8868-2374461d2fd8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019e2c54-e782-7905-8434-1ceda1329fc0" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019e2c54-e782-71bf-8868-2374461d2fd8" xlink:to="loc_dei_EntityDomain_019e2c54-e782-7905-8434-1ceda1329fc0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_UnitedAirLinesIncMember_019e2c54-e782-7b94-9d4e-f624b12cbe7e" xlink:href="ual-20260630.xsd#ual_UnitedAirLinesIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019e2c54-e782-7905-8434-1ceda1329fc0" xlink:to="loc_ual_UnitedAirLinesIncMember_019e2c54-e782-7b94-9d4e-f624b12cbe7e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019e2c54-e782-757f-8a46-e3f1f3445a04" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019e2c54-e782-7111-a958-27ec6b3557a6" xlink:to="loc_srt_ProductOrServiceAxis_019e2c54-e782-757f-8a46-e3f1f3445a04" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019e2c54-e782-757f-8a46-e3f1f3445a04_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019e2c54-e782-757f-8a46-e3f1f3445a04" xlink:to="loc_srt_ProductsAndServicesDomain_019e2c54-e782-757f-8a46-e3f1f3445a04_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019e2c54-e782-75f3-8809-6ae6db601186" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019e2c54-e782-757f-8a46-e3f1f3445a04" xlink:to="loc_srt_ProductsAndServicesDomain_019e2c54-e782-75f3-8809-6ae6db601186" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PassengerMember_019e2c54-e782-761b-ba12-fe7495541865" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PassengerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019e2c54-e782-75f3-8809-6ae6db601186" xlink:to="loc_us-gaap_PassengerMember_019e2c54-e782-761b-ba12-fe7495541865" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CargoAndFreightMember_019e2c54-e782-77bb-8d9d-c08f14b5d7f3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CargoAndFreightMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019e2c54-e782-75f3-8809-6ae6db601186" xlink:to="loc_us-gaap_CargoAndFreightMember_019e2c54-e782-77bb-8d9d-c08f14b5d7f3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductAndServiceOtherMember_019e2c54-e782-779d-a5f6-09e2a5122d80" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProductAndServiceOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019e2c54-e782-75f3-8809-6ae6db601186" xlink:to="loc_us-gaap_ProductAndServiceOtherMember_019e2c54-e782-779d-a5f6-09e2a5122d80" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesAbstract_019e2c54-e782-7e83-afdd-f1afbe8f7c2b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenuesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e782-71b0-84b2-e3347dc01272" xlink:to="loc_us-gaap_RevenuesAbstract_019e2c54-e782-7e83-afdd-f1afbe8f7c2b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019e2c54-e782-7255-9c72-f560f0dc03fb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_019e2c54-e782-7e83-afdd-f1afbe8f7c2b" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019e2c54-e782-7255-9c72-f560f0dc03fb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpensesAbstract_019e2c54-e782-7157-871f-8741f3cf5409" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CostsAndExpensesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e782-71b0-84b2-e3347dc01272" xlink:to="loc_us-gaap_CostsAndExpensesAbstract_019e2c54-e782-7157-871f-8741f3cf5409" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LaborAndRelatedExpense_019e2c54-e782-7230-a8bc-c59419369746" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LaborAndRelatedExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019e2c54-e782-7157-871f-8741f3cf5409" xlink:to="loc_us-gaap_LaborAndRelatedExpense_019e2c54-e782-7230-a8bc-c59419369746" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FuelCosts_019e2c54-e782-7fc9-a047-cb5e56300458" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FuelCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019e2c54-e782-7157-871f-8741f3cf5409" xlink:to="loc_us-gaap_FuelCosts_019e2c54-e782-7fc9-a047-cb5e56300458" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LandingFeesAndOtherRentals_019e2c54-e782-760f-9808-5826821f5c6f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LandingFeesAndOtherRentals"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019e2c54-e782-7157-871f-8741f3cf5409" xlink:to="loc_us-gaap_LandingFeesAndOtherRentals_019e2c54-e782-760f-9808-5826821f5c6f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AircraftMaintenanceMaterialsAndRepairs_019e2c54-e782-7587-a2bb-e17144c9f8bf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AircraftMaintenanceMaterialsAndRepairs"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019e2c54-e782-7157-871f-8741f3cf5409" xlink:to="loc_us-gaap_AircraftMaintenanceMaterialsAndRepairs_019e2c54-e782-7587-a2bb-e17144c9f8bf" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_019e2c54-e782-7373-830e-01ee1df811df" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DepreciationDepletionAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019e2c54-e782-7157-871f-8741f3cf5409" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_019e2c54-e782-7373-830e-01ee1df811df" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AirlineCapacityPurchaseArrangements_019e2c54-e782-76f4-a5b4-5582078eff87" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AirlineCapacityPurchaseArrangements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019e2c54-e782-7157-871f-8741f3cf5409" xlink:to="loc_us-gaap_AirlineCapacityPurchaseArrangements_019e2c54-e782-76f4-a5b4-5582078eff87" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingExpense_019e2c54-e782-79d9-bcde-3ad19246db3c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SellingExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019e2c54-e782-7157-871f-8741f3cf5409" xlink:to="loc_us-gaap_SellingExpense_019e2c54-e782-79d9-bcde-3ad19246db3c" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AircraftRental_019e2c54-e782-7ad3-83f0-6ccf19ea6335" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AircraftRental"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019e2c54-e782-7157-871f-8741f3cf5409" xlink:to="loc_us-gaap_AircraftRental_019e2c54-e782-7ad3-83f0-6ccf19ea6335" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringSettlementAndImpairmentProvisions_019e2c54-e782-7c7f-b5e8-53308c429891" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringSettlementAndImpairmentProvisions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019e2c54-e782-7157-871f-8741f3cf5409" xlink:to="loc_us-gaap_RestructuringSettlementAndImpairmentProvisions_019e2c54-e782-7c7f-b5e8-53308c429891" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCostAndExpenseOperating_019e2c54-e782-70a5-92d0-bd5942a62907" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherCostAndExpenseOperating"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019e2c54-e782-7157-871f-8741f3cf5409" xlink:to="loc_us-gaap_OtherCostAndExpenseOperating_019e2c54-e782-70a5-92d0-bd5942a62907" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpenses_019e2c54-e782-7ef3-9e21-a602ae099e92" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CostsAndExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019e2c54-e782-7157-871f-8741f3cf5409" xlink:to="loc_us-gaap_CostsAndExpenses_019e2c54-e782-7ef3-9e21-a602ae099e92" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_019e2c54-e782-7907-93d7-3c1b2b4643b4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e782-71b0-84b2-e3347dc01272" xlink:to="loc_us-gaap_OperatingIncomeLoss_019e2c54-e782-7907-93d7-3c1b2b4643b4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonoperatingIncomeExpenseAbstract_019e2c54-e782-7c40-a87c-b80a947dd431" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NonoperatingIncomeExpenseAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e782-71b0-84b2-e3347dc01272" xlink:to="loc_us-gaap_NonoperatingIncomeExpenseAbstract_019e2c54-e782-7c40-a87c-b80a947dd431" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseNonoperating_019e2c54-e782-788d-a916-f15901f9ac3e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestExpenseNonoperating"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_019e2c54-e782-7c40-a87c-b80a947dd431" xlink:to="loc_us-gaap_InterestExpenseNonoperating_019e2c54-e782-788d-a916-f15901f9ac3e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentIncomeInterest_019e2c54-e782-7485-9807-dcc4fd16af47" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentIncomeInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_019e2c54-e782-7c40-a87c-b80a947dd431" xlink:to="loc_us-gaap_InvestmentIncomeInterest_019e2c54-e782-7485-9807-dcc4fd16af47" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestCostsCapitalizedAdjustment_019e2c54-e782-7b7b-a4ce-2728bbaf8e96" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestCostsCapitalizedAdjustment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_019e2c54-e782-7c40-a87c-b80a947dd431" xlink:to="loc_us-gaap_InterestCostsCapitalizedAdjustment_019e2c54-e782-7b7b-a4ce-2728bbaf8e96" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrealizedGainLossOnInvestments_019e2c54-e782-7266-8159-20de5ae11261" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnrealizedGainLossOnInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_019e2c54-e782-7c40-a87c-b80a947dd431" xlink:to="loc_us-gaap_UnrealizedGainLossOnInvestments_019e2c54-e782-7266-8159-20de5ae11261" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_019e2c54-e782-776f-9897-7d1074188e5d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_019e2c54-e782-7c40-a87c-b80a947dd431" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_019e2c54-e782-776f-9897-7d1074188e5d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonoperatingIncomeExpense_019e2c54-e782-7f7d-86b5-0a6345870d6c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_019e2c54-e782-7c40-a87c-b80a947dd431" xlink:to="loc_us-gaap_NonoperatingIncomeExpense_019e2c54-e782-7f7d-86b5-0a6345870d6c" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019e2c54-e782-7ae5-bc92-4ee8eb1d2d04" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e782-71b0-84b2-e3347dc01272" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019e2c54-e782-7ae5-bc92-4ee8eb1d2d04" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_019e2c54-e782-7cb2-8fc1-49df2552ad35" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e782-71b0-84b2-e3347dc01272" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_019e2c54-e782-7cb2-8fc1-49df2552ad35" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019e2c54-e782-7480-9b5f-1d99e0e0196f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e782-71b0-84b2-e3347dc01272" xlink:to="loc_us-gaap_NetIncomeLoss_019e2c54-e782-7480-9b5f-1d99e0e0196f" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.unitedcontinentalholdings.com/role/STATEMENTSOFCONSOLIDATEDCOMPREHENSIVEINCOMELOSSUNAUDITEDUA" xlink:type="simple" xlink:href="ual-20260630.xsd#STATEMENTSOFCONSOLIDATEDCOMPREHENSIVEINCOMELOSSUNAUDITEDUA"/>
  <link:definitionLink xlink:role="http://www.unitedcontinentalholdings.com/role/STATEMENTSOFCONSOLIDATEDCOMPREHENSIVEINCOMELOSSUNAUDITEDUA" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019e2c54-e782-7516-b10c-293f9c7cfe0e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019e2c54-e782-7e38-b307-4b767b8c5cbb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e782-7516-b10c-293f9c7cfe0e" xlink:to="loc_us-gaap_StatementTable_019e2c54-e782-7e38-b307-4b767b8c5cbb" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019e2c54-e782-7026-9bbc-c60e43a586e6" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019e2c54-e782-7e38-b307-4b767b8c5cbb" xlink:to="loc_dei_LegalEntityAxis_019e2c54-e782-7026-9bbc-c60e43a586e6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019e2c54-e782-7026-9bbc-c60e43a586e6_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019e2c54-e782-7026-9bbc-c60e43a586e6" xlink:to="loc_dei_EntityDomain_019e2c54-e782-7026-9bbc-c60e43a586e6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019e2c54-e782-752d-929a-c1df7650ab71" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019e2c54-e782-7026-9bbc-c60e43a586e6" xlink:to="loc_dei_EntityDomain_019e2c54-e782-752d-929a-c1df7650ab71" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_UnitedAirLinesIncMember_019e2c54-e782-70ef-826e-14c82d06f415" xlink:href="ual-20260630.xsd#ual_UnitedAirLinesIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019e2c54-e782-752d-929a-c1df7650ab71" xlink:to="loc_ual_UnitedAirLinesIncMember_019e2c54-e782-70ef-826e-14c82d06f415" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019e2c54-e782-710d-90d4-97be1d1ba00b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e782-7516-b10c-293f9c7cfe0e" xlink:to="loc_us-gaap_NetIncomeLoss_019e2c54-e782-710d-90d4-97be1d1ba00b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_019e2c54-e782-7040-8e7f-261cabf5d689" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e782-7516-b10c-293f9c7cfe0e" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_019e2c54-e782-7040-8e7f-261cabf5d689" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax_019e2c54-e782-7133-881f-651f4ed0b337" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_019e2c54-e782-7040-8e7f-261cabf5d689" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax_019e2c54-e782-7133-881f-651f4ed0b337" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_OtherComprehensiveIncomeInvestmentsAndOtherNetOfTax_019e2c54-e782-73d5-8c59-4dfa4f9a4b06" xlink:href="ual-20260630.xsd#ual_OtherComprehensiveIncomeInvestmentsAndOtherNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_019e2c54-e782-7040-8e7f-261cabf5d689" xlink:to="loc_ual_OtherComprehensiveIncomeInvestmentsAndOtherNetOfTax_019e2c54-e782-73d5-8c59-4dfa4f9a4b06" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019e2c54-e782-7312-9eaa-1303fe81733f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_019e2c54-e782-7040-8e7f-261cabf5d689" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019e2c54-e782-7312-9eaa-1303fe81733f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTax_019e2c54-e782-789d-ac2a-9f64d266e120" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ComprehensiveIncomeNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e782-7516-b10c-293f9c7cfe0e" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTax_019e2c54-e782-789d-ac2a-9f64d266e120" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.unitedcontinentalholdings.com/role/CONSOLIDATEDBALANCESHEETSUNAUDITEDUA" xlink:type="simple" xlink:href="ual-20260630.xsd#CONSOLIDATEDBALANCESHEETSUNAUDITEDUA"/>
  <link:definitionLink xlink:role="http://www.unitedcontinentalholdings.com/role/CONSOLIDATEDBALANCESHEETSUNAUDITEDUA" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019e2c54-e782-7789-b6ac-5ea9d2aad0a4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019e2c54-e782-751a-9ff8-bdcfe913e388" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e782-7789-b6ac-5ea9d2aad0a4" xlink:to="loc_us-gaap_StatementTable_019e2c54-e782-751a-9ff8-bdcfe913e388" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019e2c54-e782-76b7-a5cf-7eacf8cc579c" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019e2c54-e782-751a-9ff8-bdcfe913e388" xlink:to="loc_dei_LegalEntityAxis_019e2c54-e782-76b7-a5cf-7eacf8cc579c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019e2c54-e782-76b7-a5cf-7eacf8cc579c_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019e2c54-e782-76b7-a5cf-7eacf8cc579c" xlink:to="loc_dei_EntityDomain_019e2c54-e782-76b7-a5cf-7eacf8cc579c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019e2c54-e782-712f-9d1a-c88201358eca" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019e2c54-e782-76b7-a5cf-7eacf8cc579c" xlink:to="loc_dei_EntityDomain_019e2c54-e782-712f-9d1a-c88201358eca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_UnitedAirLinesIncMember_019e2c54-e782-72d5-bc54-399921eb2b1d" xlink:href="ual-20260630.xsd#ual_UnitedAirLinesIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019e2c54-e782-712f-9d1a-c88201358eca" xlink:to="loc_ual_UnitedAirLinesIncMember_019e2c54-e782-72d5-bc54-399921eb2b1d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract_019e2c54-e782-7169-9d65-f7624667a349" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e782-7789-b6ac-5ea9d2aad0a4" xlink:to="loc_us-gaap_AssetsAbstract_019e2c54-e782-7169-9d65-f7624667a349" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019e2c54-e782-7f3f-ac43-f04a57e78a92" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019e2c54-e782-7169-9d65-f7624667a349" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019e2c54-e782-7f3f-ac43-f04a57e78a92" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermInvestments_019e2c54-e782-7e43-8ae2-8bdec783914e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShortTermInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019e2c54-e782-7169-9d65-f7624667a349" xlink:to="loc_us-gaap_ShortTermInvestments_019e2c54-e782-7e43-8ae2-8bdec783914e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReceivablesNetCurrent_019e2c54-e782-7699-ac15-f2b3d52df85e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReceivablesNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019e2c54-e782-7169-9d65-f7624667a349" xlink:to="loc_us-gaap_ReceivablesNetCurrent_019e2c54-e782-7699-ac15-f2b3d52df85e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AirlineRelatedInventoryNet_019e2c54-e782-7125-9251-131eeb77821e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AirlineRelatedInventoryNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019e2c54-e782-7169-9d65-f7624667a349" xlink:to="loc_us-gaap_AirlineRelatedInventoryNet_019e2c54-e782-7125-9251-131eeb77821e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_019e2c54-e782-7f0e-b75b-7d00f8e4d161" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PrepaidExpenseAndOtherAssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019e2c54-e782-7169-9d65-f7624667a349" xlink:to="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_019e2c54-e782-7f0e-b75b-7d00f8e4d161" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrent_019e2c54-e782-78b8-a3dd-4cb8693daf30" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019e2c54-e782-7169-9d65-f7624667a349" xlink:to="loc_us-gaap_AssetsCurrent_019e2c54-e782-78b8-a3dd-4cb8693daf30" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_019e2c54-e782-7698-8996-c1848e1a09a3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019e2c54-e782-7169-9d65-f7624667a349" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_019e2c54-e782-7698-8996-c1848e1a09a3" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAsset_019e2c54-e782-7d4a-9ff6-481e2d313c3b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseRightOfUseAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019e2c54-e782-7169-9d65-f7624667a349" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAsset_019e2c54-e782-7d4a-9ff6-481e2d313c3b" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_019e2c54-e782-79e1-a43e-23a149c7f135" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019e2c54-e782-7169-9d65-f7624667a349" xlink:to="loc_us-gaap_Goodwill_019e2c54-e782-79e1-a43e-23a149c7f135" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_019e2c54-e782-72a6-b19d-bbdf62c74636" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IntangibleAssetsNetExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019e2c54-e782-7169-9d65-f7624667a349" xlink:to="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_019e2c54-e782-72a6-b19d-bbdf62c74636" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAfterAllowanceForCreditLossNoncurrent_019e2c54-e782-7849-9e6c-fc0d8455d73b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestAfterAllowanceForCreditLossNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019e2c54-e782-7169-9d65-f7624667a349" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAfterAllowanceForCreditLossNoncurrent_019e2c54-e782-7849-9e6c-fc0d8455d73b" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsNoncurrent_019e2c54-e782-7532-91df-1c38639a6337" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019e2c54-e782-7169-9d65-f7624667a349" xlink:to="loc_us-gaap_AssetsNoncurrent_019e2c54-e782-7532-91df-1c38639a6337" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_019e2c54-e782-730e-b520-b34613967f29" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019e2c54-e782-7169-9d65-f7624667a349" xlink:to="loc_us-gaap_Assets_019e2c54-e782-730e-b520-b34613967f29" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e2c54-e782-73bf-a6c7-2a04d7946e35" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e782-7789-b6ac-5ea9d2aad0a4" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e2c54-e782-73bf-a6c7-2a04d7946e35" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableCurrent_019e2c54-e782-72ec-8ed1-326959f41b2e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccountsPayableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e2c54-e782-73bf-a6c7-2a04d7946e35" xlink:to="loc_us-gaap_AccountsPayableCurrent_019e2c54-e782-72ec-8ed1-326959f41b2e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeRelatedLiabilitiesCurrent_019e2c54-e782-7afe-9ca2-6942e2055f0e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeRelatedLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e2c54-e782-73bf-a6c7-2a04d7946e35" xlink:to="loc_us-gaap_EmployeeRelatedLiabilitiesCurrent_019e2c54-e782-7afe-9ca2-6942e2055f0e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_ContractWithCustomerLiabilityCurrentAdvanceTicketSales_019e2c54-e782-75f5-b0e2-6c9c0d460beb" xlink:href="ual-20260630.xsd#ual_ContractWithCustomerLiabilityCurrentAdvanceTicketSales"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e2c54-e782-73bf-a6c7-2a04d7946e35" xlink:to="loc_ual_ContractWithCustomerLiabilityCurrentAdvanceTicketSales_019e2c54-e782-75f5-b0e2-6c9c0d460beb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_ContractWithCustomerLiabilityCurrentFrequentFlyer_019e2c54-e782-7291-a6d3-c5924ae46a40" xlink:href="ual-20260630.xsd#ual_ContractWithCustomerLiabilityCurrentFrequentFlyer"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e2c54-e782-73bf-a6c7-2a04d7946e35" xlink:to="loc_ual_ContractWithCustomerLiabilityCurrentFrequentFlyer_019e2c54-e782-7291-a6d3-c5924ae46a40" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtAndCapitalLeaseObligationsCurrent_019e2c54-e782-7e9a-81a0-4cd68a5baf53" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebtAndCapitalLeaseObligationsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e2c54-e782-73bf-a6c7-2a04d7946e35" xlink:to="loc_us-gaap_LongTermDebtAndCapitalLeaseObligationsCurrent_019e2c54-e782-7e9a-81a0-4cd68a5baf53" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityCurrent_019e2c54-e782-7a58-b252-b93ba7123989" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e2c54-e782-73bf-a6c7-2a04d7946e35" xlink:to="loc_us-gaap_OperatingLeaseLiabilityCurrent_019e2c54-e782-7a58-b252-b93ba7123989" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesCurrent_019e2c54-e782-79f4-97e7-9d0a5f484b3a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e2c54-e782-73bf-a6c7-2a04d7946e35" xlink:to="loc_us-gaap_OtherLiabilitiesCurrent_019e2c54-e782-79f4-97e7-9d0a5f484b3a" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrent_019e2c54-e782-7a68-99a7-5930f909ddd7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e2c54-e782-73bf-a6c7-2a04d7946e35" xlink:to="loc_us-gaap_LiabilitiesCurrent_019e2c54-e782-7a68-99a7-5930f909ddd7" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtAndCapitalLeaseObligations_019e2c54-e782-77a2-8519-9444951c37ba" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebtAndCapitalLeaseObligations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e2c54-e782-73bf-a6c7-2a04d7946e35" xlink:to="loc_us-gaap_LongTermDebtAndCapitalLeaseObligations_019e2c54-e782-77a2-8519-9444951c37ba" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_019e2c54-e782-70f9-97b1-6f2b9d2f4835" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseLiabilityNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e2c54-e782-73bf-a6c7-2a04d7946e35" xlink:to="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_019e2c54-e782-70f9-97b1-6f2b9d2f4835" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_ContractWithCustomerLiabilityNoncurrentFrequentFlyer_019e2c54-e782-7be7-ac26-6726b31b5e8b" xlink:href="ual-20260630.xsd#ual_ContractWithCustomerLiabilityNoncurrentFrequentFlyer"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e2c54-e782-73bf-a6c7-2a04d7946e35" xlink:to="loc_ual_ContractWithCustomerLiabilityNoncurrentFrequentFlyer_019e2c54-e782-7be7-ac26-6726b31b5e8b" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PensionAndOtherPostretirementAndPostemploymentBenefitPlansLiabilitiesCurrentAndNoncurrent_019e2c54-e782-7f7a-9453-c1a3aa17999b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PensionAndOtherPostretirementAndPostemploymentBenefitPlansLiabilitiesCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e2c54-e782-73bf-a6c7-2a04d7946e35" xlink:to="loc_us-gaap_PensionAndOtherPostretirementAndPostemploymentBenefitPlansLiabilitiesCurrentAndNoncurrent_019e2c54-e782-7f7a-9453-c1a3aa17999b" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxLiabilitiesNet_019e2c54-e782-79f8-99e5-19e405ae10c2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredIncomeTaxLiabilitiesNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e2c54-e782-73bf-a6c7-2a04d7946e35" xlink:to="loc_us-gaap_DeferredIncomeTaxLiabilitiesNet_019e2c54-e782-79f8-99e5-19e405ae10c2" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesNoncurrent_019e2c54-e782-7b15-af43-89238b7fdbb9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherLiabilitiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e2c54-e782-73bf-a6c7-2a04d7946e35" xlink:to="loc_us-gaap_OtherLiabilitiesNoncurrent_019e2c54-e782-7b15-af43-89238b7fdbb9" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesNoncurrent_019e2c54-e782-7138-9870-625ea4cb3161" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilitiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e2c54-e782-73bf-a6c7-2a04d7946e35" xlink:to="loc_us-gaap_LiabilitiesNoncurrent_019e2c54-e782-7138-9870-625ea4cb3161" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsAndContingencies_019e2c54-e782-7add-9d4c-270a6fadbb95" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommitmentsAndContingencies"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e2c54-e782-73bf-a6c7-2a04d7946e35" xlink:to="loc_us-gaap_CommitmentsAndContingencies_019e2c54-e782-7add-9d4c-270a6fadbb95" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityAbstract_019e2c54-e782-72b4-8774-5b256406b214" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e2c54-e782-73bf-a6c7-2a04d7946e35" xlink:to="loc_us-gaap_StockholdersEquityAbstract_019e2c54-e782-72b4-8774-5b256406b214" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockValue_019e2c54-e782-7944-944c-07ad9d8d023d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_019e2c54-e782-72b4-8774-5b256406b214" xlink:to="loc_us-gaap_CommonStockValue_019e2c54-e782-7944-944c-07ad9d8d023d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalCommonStock_019e2c54-e782-73ca-a4d2-e29b49d60882" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdditionalPaidInCapitalCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_019e2c54-e782-72b4-8774-5b256406b214" xlink:to="loc_us-gaap_AdditionalPaidInCapitalCommonStock_019e2c54-e782-73ca-a4d2-e29b49d60882" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_019e2c54-e782-7e67-addc-690d7db8b76c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_019e2c54-e782-72b4-8774-5b256406b214" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_019e2c54-e782-7e67-addc-690d7db8b76c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_019e2c54-e782-7164-a1cf-5aa77897d0db" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_019e2c54-e782-72b4-8774-5b256406b214" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_019e2c54-e782-7164-a1cf-5aa77897d0db" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_PayableToShareholdersOrAffiliatesForIssuanceOfCapitalStock_019e2c54-e782-7c44-acc6-e0c13349edae" xlink:href="ual-20260630.xsd#ual_PayableToShareholdersOrAffiliatesForIssuanceOfCapitalStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_019e2c54-e782-72b4-8774-5b256406b214" xlink:to="loc_ual_PayableToShareholdersOrAffiliatesForIssuanceOfCapitalStock_019e2c54-e782-7c44-acc6-e0c13349edae" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019e2c54-e782-7e02-bfc0-90cedfbceaba" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_019e2c54-e782-72b4-8774-5b256406b214" xlink:to="loc_us-gaap_StockholdersEquity_019e2c54-e782-7e02-bfc0-90cedfbceaba" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_019e2c54-e782-70f9-b7a2-2794c81078f5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilitiesAndStockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e2c54-e782-73bf-a6c7-2a04d7946e35" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquity_019e2c54-e782-70f9-b7a2-2794c81078f5" xlink:type="arc" order="18"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.unitedcontinentalholdings.com/role/CONSOLIDATEDBALANCESHEETSUNAUDITEDUAParenthetical" xlink:type="simple" xlink:href="ual-20260630.xsd#CONSOLIDATEDBALANCESHEETSUNAUDITEDUAParenthetical"/>
  <link:definitionLink xlink:role="http://www.unitedcontinentalholdings.com/role/CONSOLIDATEDBALANCESHEETSUNAUDITEDUAParenthetical" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019e2c54-e782-76ea-ad2c-82d38279490d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019e2c54-e782-7dd1-a6f5-7a9afda661d6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e782-76ea-ad2c-82d38279490d" xlink:to="loc_us-gaap_StatementTable_019e2c54-e782-7dd1-a6f5-7a9afda661d6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019e2c54-e782-746d-a435-9ddb1298e411" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019e2c54-e782-7dd1-a6f5-7a9afda661d6" xlink:to="loc_dei_LegalEntityAxis_019e2c54-e782-746d-a435-9ddb1298e411" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019e2c54-e782-746d-a435-9ddb1298e411_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019e2c54-e782-746d-a435-9ddb1298e411" xlink:to="loc_dei_EntityDomain_019e2c54-e782-746d-a435-9ddb1298e411_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019e2c54-e782-7c06-b6ee-b54e456d0c83" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019e2c54-e782-746d-a435-9ddb1298e411" xlink:to="loc_dei_EntityDomain_019e2c54-e782-7c06-b6ee-b54e456d0c83" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_UnitedAirLinesIncMember_019e2c54-e782-7a82-8afc-c6a7cd748ec1" xlink:href="ual-20260630.xsd#ual_UnitedAirLinesIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019e2c54-e782-7c06-b6ee-b54e456d0c83" xlink:to="loc_ual_UnitedAirLinesIncMember_019e2c54-e782-7a82-8afc-c6a7cd748ec1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare_019e2c54-e782-7445-9aa2-289910bee820" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e782-76ea-ad2c-82d38279490d" xlink:to="loc_us-gaap_CommonStockParOrStatedValuePerShare_019e2c54-e782-7445-9aa2-289910bee820" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesAuthorized_019e2c54-e782-79b8-9ab6-cf9b5afd1420" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e782-76ea-ad2c-82d38279490d" xlink:to="loc_us-gaap_CommonStockSharesAuthorized_019e2c54-e782-79b8-9ab6-cf9b5afd1420" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_019e2c54-e782-7859-a450-6e094507342d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e782-76ea-ad2c-82d38279490d" xlink:to="loc_us-gaap_CommonStockSharesIssued_019e2c54-e782-7859-a450-6e094507342d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_019e2c54-e782-7b3b-85f8-409a4f4e620e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e782-76ea-ad2c-82d38279490d" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_019e2c54-e782-7b3b-85f8-409a4f4e620e" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.unitedcontinentalholdings.com/role/CONDENSEDSTATEMENTSOFCONSOLIDATEDCASHFLOWSUNAUDITEDUA" xlink:type="simple" xlink:href="ual-20260630.xsd#CONDENSEDSTATEMENTSOFCONSOLIDATEDCASHFLOWSUNAUDITEDUA"/>
  <link:definitionLink xlink:role="http://www.unitedcontinentalholdings.com/role/CONDENSEDSTATEMENTSOFCONSOLIDATEDCASHFLOWSUNAUDITEDUA" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019e2c54-e782-75ad-baa9-0c2d2753db5e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019e2c54-e782-7366-9583-900a20c7f9ac" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e782-75ad-baa9-0c2d2753db5e" xlink:to="loc_us-gaap_StatementTable_019e2c54-e782-7366-9583-900a20c7f9ac" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019e2c54-e782-7b23-8080-32bfd3c4f57b" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019e2c54-e782-7366-9583-900a20c7f9ac" xlink:to="loc_dei_LegalEntityAxis_019e2c54-e782-7b23-8080-32bfd3c4f57b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019e2c54-e782-7b23-8080-32bfd3c4f57b_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019e2c54-e782-7b23-8080-32bfd3c4f57b" xlink:to="loc_dei_EntityDomain_019e2c54-e782-7b23-8080-32bfd3c4f57b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019e2c54-e782-7822-9410-5b4761a454c7" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019e2c54-e782-7b23-8080-32bfd3c4f57b" xlink:to="loc_dei_EntityDomain_019e2c54-e782-7822-9410-5b4761a454c7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_UnitedAirLinesIncMember_019e2c54-e782-7646-80bf-f2f2861b2631" xlink:href="ual-20260630.xsd#ual_UnitedAirLinesIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019e2c54-e782-7822-9410-5b4761a454c7" xlink:to="loc_ual_UnitedAirLinesIncMember_019e2c54-e782-7646-80bf-f2f2861b2631" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_019e2c54-e782-7872-83dd-e10bbd1839fe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e782-75ad-baa9-0c2d2753db5e" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_019e2c54-e782-7872-83dd-e10bbd1839fe" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e2c54-e782-7af2-8a20-a3187700107d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_019e2c54-e782-7872-83dd-e10bbd1839fe" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019e2c54-e782-7af2-8a20-a3187700107d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_019e2c54-e782-73b1-8de9-0b311ed5ecae" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e782-75ad-baa9-0c2d2753db5e" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_019e2c54-e782-73b1-8de9-0b311ed5ecae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireProductiveAssets_019e2c54-e782-7f01-a0a3-eb27ffbdc291" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsToAcquireProductiveAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_019e2c54-e782-73b1-8de9-0b311ed5ecae" xlink:to="loc_us-gaap_PaymentsToAcquireProductiveAssets_019e2c54-e782-7f01-a0a3-eb27ffbdc291" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireShortTermInvestments_019e2c54-e782-79f4-a166-4fca0d3b60d7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsToAcquireShortTermInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_019e2c54-e782-73b1-8de9-0b311ed5ecae" xlink:to="loc_us-gaap_PaymentsToAcquireShortTermInvestments_019e2c54-e782-79f4-a166-4fca0d3b60d7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSaleMaturityAndCollectionsOfInvestments_019e2c54-e782-7d84-99fb-f11c0237bc48" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromSaleMaturityAndCollectionsOfInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_019e2c54-e782-73b1-8de9-0b311ed5ecae" xlink:to="loc_us-gaap_ProceedsFromSaleMaturityAndCollectionsOfInvestments_019e2c54-e782-7d84-99fb-f11c0237bc48" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment_019e2c54-e782-7b43-a563-3c2c2364ee05" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_019e2c54-e782-73b1-8de9-0b311ed5ecae" xlink:to="loc_us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment_019e2c54-e782-7b43-a563-3c2c2364ee05" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForProceedsFromOtherInvestingActivities_019e2c54-e782-7875-bd5e-b6355248b3dd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsForProceedsFromOtherInvestingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_019e2c54-e782-73b1-8de9-0b311ed5ecae" xlink:to="loc_us-gaap_PaymentsForProceedsFromOtherInvestingActivities_019e2c54-e782-7875-bd5e-b6355248b3dd" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019e2c54-e782-7184-af2a-35426c7e49ce" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_019e2c54-e782-73b1-8de9-0b311ed5ecae" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019e2c54-e782-7184-af2a-35426c7e49ce" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019e2c54-e782-7246-abfb-ef77f1771519" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e782-75ad-baa9-0c2d2753db5e" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019e2c54-e782-7246-abfb-ef77f1771519" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_ProceedsFromIssuanceOfLongTermDebtNet_019e2c54-e782-7e95-aec3-85536177e8a5" xlink:href="ual-20260630.xsd#ual_ProceedsFromIssuanceOfLongTermDebtNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019e2c54-e782-7246-abfb-ef77f1771519" xlink:to="loc_ual_ProceedsFromIssuanceOfLongTermDebtNet_019e2c54-e782-7e95-aec3-85536177e8a5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfLongTermDebt_019e2c54-e782-75c7-abe7-63ec2f659c20" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RepaymentsOfLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019e2c54-e782-7246-abfb-ef77f1771519" xlink:to="loc_us-gaap_RepaymentsOfLongTermDebt_019e2c54-e782-75c7-abe7-63ec2f659c20" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromPaymentsForOtherFinancingActivities_019e2c54-e782-7642-a7c1-31fb3d5bb870" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromPaymentsForOtherFinancingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019e2c54-e782-7246-abfb-ef77f1771519" xlink:to="loc_us-gaap_ProceedsFromPaymentsForOtherFinancingActivities_019e2c54-e782-7642-a7c1-31fb3d5bb870" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019e2c54-e782-7b6c-bcd5-d966b5d27a4f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019e2c54-e782-7246-abfb-ef77f1771519" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019e2c54-e782-7b6c-bcd5-d966b5d27a4f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_019e2c54-e782-79ac-869b-9b91f6d3111e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e782-75ad-baa9-0c2d2753db5e" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_019e2c54-e782-79ac-869b-9b91f6d3111e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019e2c54-e782-7e4d-b396-2a6baf5ddc66" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e782-75ad-baa9-0c2d2753db5e" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019e2c54-e782-7e4d-b396-2a6baf5ddc66" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019e2c54-e782-76de-86a2-9ccb966f0505" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_019e2c54-e782-7eaa-9653-d5159f821a55" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e782-75ad-baa9-0c2d2753db5e" xlink:to="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_019e2c54-e782-7eaa-9653-d5159f821a55" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability_019e2c54-e782-7d2e-903c-05f74f42d8ac" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_019e2c54-e782-7eaa-9653-d5159f821a55" xlink:to="loc_us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability_019e2c54-e782-7d2e-903c-05f74f42d8ac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_NoncashOrPartNoncashAcquisitionFixedAssetsAcquiredNetOfVendorCredits_019e2c54-e782-7dda-9a4d-adf7f85a2e8c" xlink:href="ual-20260630.xsd#ual_NoncashOrPartNoncashAcquisitionFixedAssetsAcquiredNetOfVendorCredits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_019e2c54-e782-7eaa-9653-d5159f821a55" xlink:to="loc_ual_NoncashOrPartNoncashAcquisitionFixedAssetsAcquiredNetOfVendorCredits_019e2c54-e782-7dda-9a4d-adf7f85a2e8c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_OperatingLeasesConvertedToFinanceLeases_019e2c54-e782-74b0-9bab-941060688f64" xlink:href="ual-20260630.xsd#ual_OperatingLeasesConvertedToFinanceLeases"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_019e2c54-e782-7eaa-9653-d5159f821a55" xlink:to="loc_ual_OperatingLeasesConvertedToFinanceLeases_019e2c54-e782-74b0-9bab-941060688f64" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherSignificantNoncashTransactionValueOfConsiderationReceived1_019e2c54-e782-7e5f-836c-5893758f5c08" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherSignificantNoncashTransactionValueOfConsiderationReceived1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_019e2c54-e782-7eaa-9653-d5159f821a55" xlink:to="loc_us-gaap_OtherSignificantNoncashTransactionValueOfConsiderationReceived1_019e2c54-e782-7e5f-836c-5893758f5c08" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.unitedcontinentalholdings.com/role/CONDENSEDSTATEMENTSOFCONSOLIDATEDCASHFLOWSUNAUDITEDUAParenthetical" xlink:type="simple" xlink:href="ual-20260630.xsd#CONDENSEDSTATEMENTSOFCONSOLIDATEDCASHFLOWSUNAUDITEDUAParenthetical"/>
  <link:definitionLink xlink:role="http://www.unitedcontinentalholdings.com/role/CONDENSEDSTATEMENTSOFCONSOLIDATEDCASHFLOWSUNAUDITEDUAParenthetical" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019e2c54-e782-7027-b430-7d919adbf008" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019e2c54-e782-77b9-96a9-cf8a1fb622bb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e782-7027-b430-7d919adbf008" xlink:to="loc_us-gaap_StatementTable_019e2c54-e782-77b9-96a9-cf8a1fb622bb" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019e2c54-e782-7bed-9a5e-c0044cee0cee" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019e2c54-e782-77b9-96a9-cf8a1fb622bb" xlink:to="loc_dei_LegalEntityAxis_019e2c54-e782-7bed-9a5e-c0044cee0cee" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019e2c54-e782-7bed-9a5e-c0044cee0cee_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019e2c54-e782-7bed-9a5e-c0044cee0cee" xlink:to="loc_dei_EntityDomain_019e2c54-e782-7bed-9a5e-c0044cee0cee_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019e2c54-e782-7adb-8057-688cd3466c83" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019e2c54-e782-7bed-9a5e-c0044cee0cee" xlink:to="loc_dei_EntityDomain_019e2c54-e782-7adb-8057-688cd3466c83" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_UnitedAirLinesIncMember_019e2c54-e782-7e58-8379-0adbf1c2c729" xlink:href="ual-20260630.xsd#ual_UnitedAirLinesIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019e2c54-e782-7adb-8057-688cd3466c83" xlink:to="loc_ual_UnitedAirLinesIncMember_019e2c54-e782-7e58-8379-0adbf1c2c729" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAbstract_019e2c54-e782-76f8-bc71-d371fa17049a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e782-7027-b430-7d919adbf008" xlink:to="loc_us-gaap_CashAndCashEquivalentsAbstract_019e2c54-e782-76f8-bc71-d371fa17049a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019e2c54-e782-78f0-9da2-97e566d2344d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsAbstract_019e2c54-e782-76f8-bc71-d371fa17049a" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019e2c54-e782-78f0-9da2-97e566d2344d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashCurrent_019e2c54-e782-7caa-a28b-cd823c81aadf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedCashCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsAbstract_019e2c54-e782-76f8-bc71-d371fa17049a" xlink:to="loc_us-gaap_RestrictedCashCurrent_019e2c54-e782-7caa-a28b-cd823c81aadf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashNoncurrent_019e2c54-e782-7cac-9242-7493c299045c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedCashNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsAbstract_019e2c54-e782-76f8-bc71-d371fa17049a" xlink:to="loc_us-gaap_RestrictedCashNoncurrent_019e2c54-e782-7cac-9242-7493c299045c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019e2c54-e782-745b-a50f-a570407abf7c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsAbstract_019e2c54-e782-76f8-bc71-d371fa17049a" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019e2c54-e782-745b-a50f-a570407abf7c" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.unitedcontinentalholdings.com/role/STATEMENTSOFCONSOLIDATEDSTOCKHOLDERSEQUITYUNAUDITEDUA" xlink:type="simple" xlink:href="ual-20260630.xsd#STATEMENTSOFCONSOLIDATEDSTOCKHOLDERSEQUITYUNAUDITEDUA"/>
  <link:definitionLink xlink:role="http://www.unitedcontinentalholdings.com/role/STATEMENTSOFCONSOLIDATEDSTOCKHOLDERSEQUITYUNAUDITEDUA" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019e2c54-e782-7388-b8d9-468512267ff2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019e2c54-e782-7706-baa4-4a75b84a6e61" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e782-7388-b8d9-468512267ff2" xlink:to="loc_us-gaap_StatementTable_019e2c54-e782-7706-baa4-4a75b84a6e61" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019e2c54-e782-793a-bb03-8e600ecce507" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019e2c54-e782-7706-baa4-4a75b84a6e61" xlink:to="loc_dei_LegalEntityAxis_019e2c54-e782-793a-bb03-8e600ecce507" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019e2c54-e782-793a-bb03-8e600ecce507_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019e2c54-e782-793a-bb03-8e600ecce507" xlink:to="loc_dei_EntityDomain_019e2c54-e782-793a-bb03-8e600ecce507_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019e2c54-e782-739a-b8f0-e28813cbb76f" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019e2c54-e782-793a-bb03-8e600ecce507" xlink:to="loc_dei_EntityDomain_019e2c54-e782-739a-b8f0-e28813cbb76f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_UnitedAirLinesIncMember_019e2c54-e782-79a9-bd0c-eaa33f6781d3" xlink:href="ual-20260630.xsd#ual_UnitedAirLinesIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019e2c54-e782-739a-b8f0-e28813cbb76f" xlink:to="loc_ual_UnitedAirLinesIncMember_019e2c54-e782-79a9-bd0c-eaa33f6781d3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019e2c54-e782-714c-b749-72218cc5154d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019e2c54-e782-7706-baa4-4a75b84a6e61" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019e2c54-e782-714c-b749-72218cc5154d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019e2c54-e782-714c-b749-72218cc5154d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019e2c54-e782-714c-b749-72218cc5154d" xlink:to="loc_us-gaap_EquityComponentDomain_019e2c54-e782-714c-b749-72218cc5154d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019e2c54-e782-7b2f-b77b-3377ec5c1b4b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019e2c54-e782-714c-b749-72218cc5154d" xlink:to="loc_us-gaap_EquityComponentDomain_019e2c54-e782-7b2f-b77b-3377ec5c1b4b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_019e2c54-e782-7fc9-915a-112b24ea6aad" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019e2c54-e782-7b2f-b77b-3377ec5c1b4b" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_019e2c54-e782-7fc9-915a-112b24ea6aad" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_019e2c54-e782-78f7-8f68-54e86de6bd94" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019e2c54-e782-7b2f-b77b-3377ec5c1b4b" xlink:to="loc_us-gaap_RetainedEarningsMember_019e2c54-e782-78f7-8f68-54e86de6bd94" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019e2c54-e782-75d2-b016-b607afa51143" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019e2c54-e782-7b2f-b77b-3377ec5c1b4b" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019e2c54-e782-75d2-b016-b607afa51143" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReceivablesFromStockholderMember_019e2c54-e782-7872-8bdf-f9fbf96d6bf4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReceivablesFromStockholderMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019e2c54-e782-7b2f-b77b-3377ec5c1b4b" xlink:to="loc_us-gaap_ReceivablesFromStockholderMember_019e2c54-e782-7872-8bdf-f9fbf96d6bf4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e2c54-e782-77cb-8253-b313d3e5a7d9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e2c54-e782-7388-b8d9-468512267ff2" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e2c54-e782-77cb-8253-b313d3e5a7d9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019e2c54-e782-7c20-be35-8b496b8607fe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e2c54-e782-77cb-8253-b313d3e5a7d9" xlink:to="loc_us-gaap_StockholdersEquity_019e2c54-e782-7c20-be35-8b496b8607fe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019e2c54-e782-778a-b51c-ebee781de802" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e2c54-e782-77cb-8253-b313d3e5a7d9" xlink:to="loc_us-gaap_NetIncomeLoss_019e2c54-e782-778a-b51c-ebee781de802" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019e2c54-e782-705b-948d-c194796c8576" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e2c54-e782-77cb-8253-b313d3e5a7d9" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019e2c54-e782-705b-948d-c194796c8576" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_019e2c54-e782-7252-8547-53574b2fd641" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e2c54-e782-77cb-8253-b313d3e5a7d9" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_019e2c54-e782-7252-8547-53574b2fd641" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodValue_019e2c54-e782-700b-93d1-ed1e4de24875" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockRepurchasedDuringPeriodValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e2c54-e782-77cb-8253-b313d3e5a7d9" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodValue_019e2c54-e782-700b-93d1-ed1e4de24875" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityOther_019e2c54-e782-7483-b2c8-54d98aa41cfd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquityOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e2c54-e782-77cb-8253-b313d3e5a7d9" xlink:to="loc_us-gaap_StockholdersEquityOther_019e2c54-e782-7483-b2c8-54d98aa41cfd" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019e2c54-e782-764b-b194-4b2eb2eb5be6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquity"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.unitedcontinentalholdings.com/role/REVENUERECOGNITIONScheduleofOperatingRevenuebyGeographicRegionDetails" xlink:type="simple" xlink:href="ual-20260630.xsd#REVENUERECOGNITIONScheduleofOperatingRevenuebyGeographicRegionDetails"/>
  <link:definitionLink xlink:role="http://www.unitedcontinentalholdings.com/role/REVENUERECOGNITIONScheduleofOperatingRevenuebyGeographicRegionDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_019e2c54-e782-7993-93fe-43855d4a6025" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_019e2c54-e782-7aa0-9056-d3a4bab17e34" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019e2c54-e782-7993-93fe-43855d4a6025" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_019e2c54-e782-7aa0-9056-d3a4bab17e34" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AirlineDestinationsAxis_019e2c54-e782-7212-97cb-d68e647d147f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AirlineDestinationsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019e2c54-e782-7aa0-9056-d3a4bab17e34" xlink:to="loc_us-gaap_AirlineDestinationsAxis_019e2c54-e782-7212-97cb-d68e647d147f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AirlineDestinationDomain_019e2c54-e782-7212-97cb-d68e647d147f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AirlineDestinationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AirlineDestinationsAxis_019e2c54-e782-7212-97cb-d68e647d147f" xlink:to="loc_us-gaap_AirlineDestinationDomain_019e2c54-e782-7212-97cb-d68e647d147f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AirlineDestinationDomain_019e2c54-e782-7dfb-a07f-58dd0bf3f937" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AirlineDestinationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AirlineDestinationsAxis_019e2c54-e782-7212-97cb-d68e647d147f" xlink:to="loc_us-gaap_AirlineDestinationDomain_019e2c54-e782-7dfb-a07f-58dd0bf3f937" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DomesticDestinationMember_019e2c54-e782-7b5a-9080-ccdb98b949b6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DomesticDestinationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AirlineDestinationDomain_019e2c54-e782-7dfb-a07f-58dd0bf3f937" xlink:to="loc_us-gaap_DomesticDestinationMember_019e2c54-e782-7b5a-9080-ccdb98b949b6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AtlanticDestinationMember_019e2c54-e782-7c34-b53e-304ac824cbba" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AtlanticDestinationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AirlineDestinationDomain_019e2c54-e782-7dfb-a07f-58dd0bf3f937" xlink:to="loc_us-gaap_AtlanticDestinationMember_019e2c54-e782-7c34-b53e-304ac824cbba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PacificDestinationMember_019e2c54-e782-7357-b254-5b7d72e6f7e7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PacificDestinationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AirlineDestinationDomain_019e2c54-e782-7dfb-a07f-58dd0bf3f937" xlink:to="loc_us-gaap_PacificDestinationMember_019e2c54-e782-7357-b254-5b7d72e6f7e7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LatinAmericaDestinationMember_019e2c54-e782-7dfa-a201-9f4eb226867c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LatinAmericaDestinationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AirlineDestinationDomain_019e2c54-e782-7dfb-a07f-58dd0bf3f937" xlink:to="loc_us-gaap_LatinAmericaDestinationMember_019e2c54-e782-7dfa-a201-9f4eb226867c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019e2c54-e782-78eb-a271-2bd5321fe91d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019e2c54-e782-7993-93fe-43855d4a6025" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019e2c54-e782-78eb-a271-2bd5321fe91d" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.unitedcontinentalholdings.com/role/REVENUERECOGNITIONNarrativeDetails" xlink:type="simple" xlink:href="ual-20260630.xsd#REVENUERECOGNITIONNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.unitedcontinentalholdings.com/role/REVENUERECOGNITIONNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ual_RevenueFromContractWithCustomerLineItems_019e2c54-e782-7e92-9898-4eebbd997085" xlink:href="ual-20260630.xsd#ual_RevenueFromContractWithCustomerLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_RevenueFromContractWithCustomerTable_019e2c54-e782-7973-9027-e1f2326db519" xlink:href="ual-20260630.xsd#ual_RevenueFromContractWithCustomerTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_ual_RevenueFromContractWithCustomerLineItems_019e2c54-e782-7e92-9898-4eebbd997085" xlink:to="loc_ual_RevenueFromContractWithCustomerTable_019e2c54-e782-7973-9027-e1f2326db519" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019e2c54-e782-7eef-a726-f396ef38a8bb" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ual_RevenueFromContractWithCustomerTable_019e2c54-e782-7973-9027-e1f2326db519" xlink:to="loc_srt_ProductOrServiceAxis_019e2c54-e782-7eef-a726-f396ef38a8bb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019e2c54-e782-7eef-a726-f396ef38a8bb_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019e2c54-e782-7eef-a726-f396ef38a8bb" xlink:to="loc_srt_ProductsAndServicesDomain_019e2c54-e782-7eef-a726-f396ef38a8bb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019e2c54-e782-767b-8b13-dce78108aab9" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019e2c54-e782-7eef-a726-f396ef38a8bb" xlink:to="loc_srt_ProductsAndServicesDomain_019e2c54-e782-767b-8b13-dce78108aab9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_PassengerAdvanceTicketSalesMember_019e2c54-e782-752a-9205-e00aae3effda" xlink:href="ual-20260630.xsd#ual_PassengerAdvanceTicketSalesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019e2c54-e782-767b-8b13-dce78108aab9" xlink:to="loc_ual_PassengerAdvanceTicketSalesMember_019e2c54-e782-752a-9205-e00aae3effda" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_PassengerAncillaryFeesMember_019e2c54-e782-7ec5-a513-bec8a7602024" xlink:href="ual-20260630.xsd#ual_PassengerAncillaryFeesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019e2c54-e782-767b-8b13-dce78108aab9" xlink:to="loc_ual_PassengerAncillaryFeesMember_019e2c54-e782-7ec5-a513-bec8a7602024" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductAndServiceOtherMember_019e2c54-e782-7a98-8cb1-7c445a1de026" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProductAndServiceOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019e2c54-e782-767b-8b13-dce78108aab9" xlink:to="loc_us-gaap_ProductAndServiceOtherMember_019e2c54-e782-7a98-8cb1-7c445a1de026" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfArrangementAxis_019e2c54-e782-7ae4-ac00-76a8b26c573e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TypeOfArrangementAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ual_RevenueFromContractWithCustomerTable_019e2c54-e782-7973-9027-e1f2326db519" xlink:to="loc_us-gaap_TypeOfArrangementAxis_019e2c54-e782-7ae4-ac00-76a8b26c573e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_019e2c54-e782-7ae4-ac00-76a8b26c573e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ArrangementsAndNonarrangementTransactionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_TypeOfArrangementAxis_019e2c54-e782-7ae4-ac00-76a8b26c573e" xlink:to="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_019e2c54-e782-7ae4-ac00-76a8b26c573e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_019e2c54-e782-7840-93f9-c57e5cd5e8fd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ArrangementsAndNonarrangementTransactionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_TypeOfArrangementAxis_019e2c54-e782-7ae4-ac00-76a8b26c573e" xlink:to="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_019e2c54-e782-7840-93f9-c57e5cd5e8fd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_ChaseAndOtherPartnerAgreementsMember_019e2c54-e782-73a3-9e63-06973065ee76" xlink:href="ual-20260630.xsd#ual_ChaseAndOtherPartnerAgreementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_019e2c54-e782-7840-93f9-c57e5cd5e8fd" xlink:to="loc_ual_ChaseAndOtherPartnerAgreementsMember_019e2c54-e782-73a3-9e63-06973065ee76" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_019e2c54-e782-73d1-b56b-1653906a9e02" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ContractWithCustomerLiabilityRevenueRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ual_RevenueFromContractWithCustomerLineItems_019e2c54-e782-7e92-9898-4eebbd997085" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_019e2c54-e782-73d1-b56b-1653906a9e02" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019e2c54-e782-7842-94de-1a3e85c1ec7c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ual_RevenueFromContractWithCustomerLineItems_019e2c54-e782-7e92-9898-4eebbd997085" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019e2c54-e782-7842-94de-1a3e85c1ec7c" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.unitedcontinentalholdings.com/role/REVENUERECOGNITIONRollForwardofFrequentFlyerDeferredRevenueDetails" xlink:type="simple" xlink:href="ual-20260630.xsd#REVENUERECOGNITIONRollForwardofFrequentFlyerDeferredRevenueDetails"/>
  <link:definitionLink xlink:role="http://www.unitedcontinentalholdings.com/role/REVENUERECOGNITIONRollForwardofFrequentFlyerDeferredRevenueDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_019e2c54-e782-7932-837b-30e1aa8def61" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_019e2c54-e782-7e6c-9b87-ae75d236393d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019e2c54-e782-7932-837b-30e1aa8def61" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_019e2c54-e782-7e6c-9b87-ae75d236393d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019e2c54-e782-7766-b8f9-68c25a2ab09b" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019e2c54-e782-7e6c-9b87-ae75d236393d" xlink:to="loc_srt_ProductOrServiceAxis_019e2c54-e782-7766-b8f9-68c25a2ab09b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019e2c54-e782-7766-b8f9-68c25a2ab09b_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019e2c54-e782-7766-b8f9-68c25a2ab09b" xlink:to="loc_srt_ProductsAndServicesDomain_019e2c54-e782-7766-b8f9-68c25a2ab09b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019e2c54-e782-7af2-9bc0-9ef630e0064e" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019e2c54-e782-7766-b8f9-68c25a2ab09b" xlink:to="loc_srt_ProductsAndServicesDomain_019e2c54-e782-7af2-9bc0-9ef630e0064e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_FrequentFlyerProgramMember_019e2c54-e782-7b7a-8275-6a27bad5a750" xlink:href="ual-20260630.xsd#ual_FrequentFlyerProgramMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019e2c54-e782-7af2-9bc0-9ef630e0064e" xlink:to="loc_ual_FrequentFlyerProgramMember_019e2c54-e782-7b7a-8275-6a27bad5a750" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_MovementInContractWithCustomerLiabilityRollForward_019e2c54-e782-79da-842b-985e1c694e20" xlink:href="ual-20260630.xsd#ual_MovementInContractWithCustomerLiabilityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019e2c54-e782-7932-837b-30e1aa8def61" xlink:to="loc_ual_MovementInContractWithCustomerLiabilityRollForward_019e2c54-e782-79da-842b-985e1c694e20" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiability_019e2c54-e782-79af-98d7-3d73214b0f44" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ContractWithCustomerLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ual_MovementInContractWithCustomerLiabilityRollForward_019e2c54-e782-79da-842b-985e1c694e20" xlink:to="loc_us-gaap_ContractWithCustomerLiability_019e2c54-e782-79af-98d7-3d73214b0f44" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_FrequentFlyerMileageMilesAwardedInPeriod_019e2c54-e782-7287-9529-7d82577dd1bd" xlink:href="ual-20260630.xsd#ual_FrequentFlyerMileageMilesAwardedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ual_MovementInContractWithCustomerLiabilityRollForward_019e2c54-e782-79da-842b-985e1c694e20" xlink:to="loc_ual_FrequentFlyerMileageMilesAwardedInPeriod_019e2c54-e782-7287-9529-7d82577dd1bd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_TravelMilesRedemptionFrequentFlyerDeferredRevenue_019e2c54-e782-7cdb-95ee-ece0440e580c" xlink:href="ual-20260630.xsd#ual_TravelMilesRedemptionFrequentFlyerDeferredRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ual_MovementInContractWithCustomerLiabilityRollForward_019e2c54-e782-79da-842b-985e1c694e20" xlink:to="loc_ual_TravelMilesRedemptionFrequentFlyerDeferredRevenue_019e2c54-e782-7cdb-95ee-ece0440e580c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_NonTravelMilesRedemptionFrequentFlyerDeferredRevenue_019e2c54-e782-772e-a5ad-b434348e99ef" xlink:href="ual-20260630.xsd#ual_NonTravelMilesRedemptionFrequentFlyerDeferredRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ual_MovementInContractWithCustomerLiabilityRollForward_019e2c54-e782-79da-842b-985e1c694e20" xlink:to="loc_ual_NonTravelMilesRedemptionFrequentFlyerDeferredRevenue_019e2c54-e782-772e-a5ad-b434348e99ef" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiability_019e2c54-e782-7b9c-9025-950c5a581c1b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ContractWithCustomerLiability"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.unitedcontinentalholdings.com/role/EARNINGSPERSHARENarrativeDetails" xlink:type="simple" xlink:href="ual-20260630.xsd#EARNINGSPERSHARENarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.unitedcontinentalholdings.com/role/EARNINGSPERSHARENarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockLineItems_019e2c54-e782-70fb-bc95-b2fee8548ba6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_019e2c54-e782-70f0-bae1-79a1f7568614" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfStockByClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_019e2c54-e782-70fb-bc95-b2fee8548ba6" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_019e2c54-e782-70f0-bae1-79a1f7568614" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019e2c54-e782-7271-9336-0e8a026b8d46" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_019e2c54-e782-70f0-bae1-79a1f7568614" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019e2c54-e782-7271-9336-0e8a026b8d46" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019e2c54-e782-7271-9336-0e8a026b8d46_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019e2c54-e782-7271-9336-0e8a026b8d46" xlink:to="loc_us-gaap_ClassOfStockDomain_019e2c54-e782-7271-9336-0e8a026b8d46_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019e2c54-e782-7af7-9edb-4a8416314e16" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019e2c54-e782-7271-9336-0e8a026b8d46" xlink:to="loc_us-gaap_ClassOfStockDomain_019e2c54-e782-7af7-9edb-4a8416314e16" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_019e2c54-e782-7d12-8bbb-ba93369825bb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019e2c54-e782-7af7-9edb-4a8416314e16" xlink:to="loc_us-gaap_CommonStockMember_019e2c54-e782-7d12-8bbb-ba93369825bb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_019ea717-47b5-79b5-bd26-13894c2c8f45" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_019e2c54-e782-70f0-bae1-79a1f7568614" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_019ea717-47b5-79b5-bd26-13894c2c8f45" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019ea717-47b5-79b5-bd26-13894c2c8f45_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_019ea717-47b5-79b5-bd26-13894c2c8f45" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019ea717-47b5-79b5-bd26-13894c2c8f45_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019ea717-47b5-7b26-973f-50a944458aae" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_019ea717-47b5-79b5-bd26-13894c2c8f45" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019ea717-47b5-7b26-973f-50a944458aae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_019ea717-671c-70c8-ab16-e0e05a2863bc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_019ea717-47b5-7b26-973f-50a944458aae" xlink:to="loc_us-gaap_SubsequentEventMember_019ea717-671c-70c8-ab16-e0e05a2863bc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_019e2c54-e782-7bb3-a1d2-53cd46bf9696" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019e2c54-e782-70fb-bc95-b2fee8548ba6" xlink:to="loc_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_019e2c54-e782-7bb3-a1d2-53cd46bf9696" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_StockIssuedDuringPeriodSharesNetShareSettlementFromWarrantsExercised_019e2c54-e782-774d-99ba-0cf128a0c336" xlink:href="ual-20260630.xsd#ual_StockIssuedDuringPeriodSharesNetShareSettlementFromWarrantsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019e2c54-e782-70fb-bc95-b2fee8548ba6" xlink:to="loc_ual_StockIssuedDuringPeriodSharesNetShareSettlementFromWarrantsExercised_019e2c54-e782-774d-99ba-0cf128a0c336" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StockRepurchaseProgramAuthorizedAmount1_019f674c-308c-748e-a5ce-a5dfd1061086" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StockRepurchaseProgramAuthorizedAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019e2c54-e782-70fb-bc95-b2fee8548ba6" xlink:to="loc_srt_StockRepurchaseProgramAuthorizedAmount1_019f674c-308c-748e-a5ce-a5dfd1061086" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockSharesAcquired_019e2c54-e782-748b-8926-548c461b0c86" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockSharesAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019e2c54-e782-70fb-bc95-b2fee8548ba6" xlink:to="loc_us-gaap_TreasuryStockSharesAcquired_019e2c54-e782-748b-8926-548c461b0c86" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_019e2c54-e782-7771-be63-30f475b6c268" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockValueAcquiredCostMethod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019e2c54-e782-70fb-bc95-b2fee8548ba6" xlink:to="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_019e2c54-e782-7771-be63-30f475b6c268" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1_019e2c54-e782-76f9-b34f-486c6e1778d8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019e2c54-e782-70fb-bc95-b2fee8548ba6" xlink:to="loc_us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1_019e2c54-e782-76f9-b34f-486c6e1778d8" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.unitedcontinentalholdings.com/role/ACCUMULATEDOTHERCOMPREHENSIVEINCOMELOSSDetails" xlink:type="simple" xlink:href="ual-20260630.xsd#ACCUMULATEDOTHERCOMPREHENSIVEINCOMELOSSDetails"/>
  <link:definitionLink xlink:role="http://www.unitedcontinentalholdings.com/role/ACCUMULATEDOTHERCOMPREHENSIVEINCOMELOSSDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019e2c54-e84c-7310-982e-ebc78b4973da" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_019e2c54-e84c-7803-9fc9-32b2a085b640" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019e2c54-e84c-7310-982e-ebc78b4973da" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_019e2c54-e84c-7803-9fc9-32b2a085b640" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019e2c54-e84c-7a25-b06b-7f61dcabbe73" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_019e2c54-e84c-7803-9fc9-32b2a085b640" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019e2c54-e84c-7a25-b06b-7f61dcabbe73" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019e2c54-e84c-7a25-b06b-7f61dcabbe73_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019e2c54-e84c-7a25-b06b-7f61dcabbe73" xlink:to="loc_us-gaap_EquityComponentDomain_019e2c54-e84c-7a25-b06b-7f61dcabbe73_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019e2c54-e84c-70e4-b6df-98dd6945ddc4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019e2c54-e84c-7a25-b06b-7f61dcabbe73" xlink:to="loc_us-gaap_EquityComponentDomain_019e2c54-e84c-70e4-b6df-98dd6945ddc4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019e2c54-e84c-730f-919d-320f12a37575" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019e2c54-e84c-70e4-b6df-98dd6945ddc4" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019e2c54-e84c-730f-919d-320f12a37575" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_019e2c54-e84c-775c-8ac7-23d6d4877800" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019e2c54-e84c-730f-919d-320f12a37575" xlink:to="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_019e2c54-e84c-775c-8ac7-23d6d4877800" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_019e2c54-e84c-7f02-97db-e8e959ee7a22" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019e2c54-e84c-730f-919d-320f12a37575" xlink:to="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_019e2c54-e84c-7f02-97db-e8e959ee7a22" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_AOCIAttributableToParentBeforeTaxRollForward_019e2c54-e84c-7140-88c5-6b9ab7c3a414" xlink:href="ual-20260630.xsd#ual_AOCIAttributableToParentBeforeTaxRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019e2c54-e84c-7310-982e-ebc78b4973da" xlink:to="loc_ual_AOCIAttributableToParentBeforeTaxRollForward_019e2c54-e84c-7140-88c5-6b9ab7c3a414" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AociBeforeTaxAttributableToParent_019e2c54-e84c-761c-a234-fd5019f1db63" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AociBeforeTaxAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ual_AOCIAttributableToParentBeforeTaxRollForward_019e2c54-e84c-7140-88c5-6b9ab7c3a414" xlink:to="loc_us-gaap_AociBeforeTaxAttributableToParent_019e2c54-e84c-761c-a234-fd5019f1db63" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OciBeforeReclassificationsBeforeTaxAttributableToParent_019e2c54-e84c-7293-9485-be35a4b0be4a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OciBeforeReclassificationsBeforeTaxAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ual_AOCIAttributableToParentBeforeTaxRollForward_019e2c54-e84c-7140-88c5-6b9ab7c3a414" xlink:to="loc_us-gaap_OciBeforeReclassificationsBeforeTaxAttributableToParent_019e2c54-e84c-7293-9485-be35a4b0be4a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAociCurrentPeriodBeforeTaxAttributableToParent_019e2c54-e84c-79b1-b03d-193f0fa08a72" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReclassificationFromAociCurrentPeriodBeforeTaxAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ual_AOCIAttributableToParentBeforeTaxRollForward_019e2c54-e84c-7140-88c5-6b9ab7c3a414" xlink:to="loc_us-gaap_ReclassificationFromAociCurrentPeriodBeforeTaxAttributableToParent_019e2c54-e84c-79b1-b03d-193f0fa08a72" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AociBeforeTaxAttributableToParent_019e2c54-e84c-7ef2-b3c4-7fead7574075" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AociBeforeTaxAttributableToParent"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_AOCIAttributableToParentTaxRollForward_019e2c54-e84c-7b39-982e-0bfbb107fdef" xlink:href="ual-20260630.xsd#ual_AOCIAttributableToParentTaxRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019e2c54-e84c-7310-982e-ebc78b4973da" xlink:to="loc_ual_AOCIAttributableToParentTaxRollForward_019e2c54-e84c-7b39-982e-0bfbb107fdef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AociTaxAttributableToParent_019e2c54-e84c-723f-be78-5ed77ae9d88b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AociTaxAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ual_AOCIAttributableToParentTaxRollForward_019e2c54-e84c-7b39-982e-0bfbb107fdef" xlink:to="loc_us-gaap_AociTaxAttributableToParent_019e2c54-e84c-723f-be78-5ed77ae9d88b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsTax_019e2c54-e84c-7f45-8ad2-8e34edef6347" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ual_AOCIAttributableToParentTaxRollForward_019e2c54-e84c-7b39-982e-0bfbb107fdef" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsTax_019e2c54-e84c-7f45-8ad2-8e34edef6347" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAociCurrentPeriodTax_019e2c54-e84c-7828-beeb-ff15c8dcab4a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReclassificationFromAociCurrentPeriodTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ual_AOCIAttributableToParentTaxRollForward_019e2c54-e84c-7b39-982e-0bfbb107fdef" xlink:to="loc_us-gaap_ReclassificationFromAociCurrentPeriodTax_019e2c54-e84c-7828-beeb-ff15c8dcab4a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AociTaxAttributableToParent_019e2c54-e84c-7c89-8f33-c68fa45122e2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AociTaxAttributableToParent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019e2c54-e84c-78cd-9bf1-3fdcdc8c486f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AOCIAttributableToParentNetOfTaxRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019e2c54-e84c-7310-982e-ebc78b4973da" xlink:to="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019e2c54-e84c-78cd-9bf1-3fdcdc8c486f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019e2c54-e84c-71ac-9701-8a4bce2391da" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019e2c54-e84c-78cd-9bf1-3fdcdc8c486f" xlink:to="loc_us-gaap_StockholdersEquity_019e2c54-e84c-71ac-9701-8a4bce2391da" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OciBeforeReclassificationsNetOfTaxAttributableToParent_019e2c54-e84c-75a1-b382-88b3f2513504" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OciBeforeReclassificationsNetOfTaxAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019e2c54-e84c-78cd-9bf1-3fdcdc8c486f" xlink:to="loc_us-gaap_OciBeforeReclassificationsNetOfTaxAttributableToParent_019e2c54-e84c-75a1-b382-88b3f2513504" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent_019e2c54-e84c-7f28-b298-6d848a3bf033" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019e2c54-e84c-78cd-9bf1-3fdcdc8c486f" xlink:to="loc_us-gaap_ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent_019e2c54-e84c-7f28-b298-6d848a3bf033" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019e2c54-e84c-7952-a9cd-7695b9fbdc07" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxesAndTaxCredits_019e2c54-e84c-7e06-9a04-9fac0b1aae59" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredIncomeTaxesAndTaxCredits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019e2c54-e84c-7310-982e-ebc78b4973da" xlink:to="loc_us-gaap_DeferredIncomeTaxesAndTaxCredits_019e2c54-e84c-7e06-9a04-9fac0b1aae59" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.unitedcontinentalholdings.com/role/PENSIONANDOTHERPOSTRETIREMENTBENEFITPLANSScheduleofComponentsofNetPeriodicBenefitCostDetails" xlink:type="simple" xlink:href="ual-20260630.xsd#PENSIONANDOTHERPOSTRETIREMENTBENEFITPLANSScheduleofComponentsofNetPeriodicBenefitCostDetails"/>
  <link:definitionLink xlink:role="http://www.unitedcontinentalholdings.com/role/PENSIONANDOTHERPOSTRETIREMENTBENEFITPLANSScheduleofComponentsofNetPeriodicBenefitCostDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019e2c54-e84c-7236-9b29-32c6ed37b33e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_019e2c54-e84c-70db-9121-c8c38b2f26b1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019e2c54-e84c-7236-9b29-32c6ed37b33e" xlink:to="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_019e2c54-e84c-70db-9121-c8c38b2f26b1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeAxis_019e2c54-e84c-7821-bd12-2604a65fe17e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RetirementPlanTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_019e2c54-e84c-70db-9121-c8c38b2f26b1" xlink:to="loc_us-gaap_RetirementPlanTypeAxis_019e2c54-e84c-7821-bd12-2604a65fe17e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_019e2c54-e84c-7821-bd12-2604a65fe17e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_019e2c54-e84c-7821-bd12-2604a65fe17e" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_019e2c54-e84c-7821-bd12-2604a65fe17e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_019e2c54-e84c-708b-98a3-03e42685d6fa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_019e2c54-e84c-7821-bd12-2604a65fe17e" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_019e2c54-e84c-708b-98a3-03e42685d6fa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PensionPlansDefinedBenefitMember_019e2c54-e84c-7192-a28c-229427c82e63" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PensionPlansDefinedBenefitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_019e2c54-e84c-708b-98a3-03e42685d6fa" xlink:to="loc_us-gaap_PensionPlansDefinedBenefitMember_019e2c54-e84c-7192-a28c-229427c82e63" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember_019e2c54-e84c-723d-b944-3bb4c0583b1f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_019e2c54-e84c-708b-98a3-03e42685d6fa" xlink:to="loc_us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember_019e2c54-e84c-723d-b944-3bb4c0583b1f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanServiceCost_019e2c54-e84c-7ecc-bdca-41f0a839ba89" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DefinedBenefitPlanServiceCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019e2c54-e84c-7236-9b29-32c6ed37b33e" xlink:to="loc_us-gaap_DefinedBenefitPlanServiceCost_019e2c54-e84c-7ecc-bdca-41f0a839ba89" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanInterestCost_019e2c54-e84c-7342-b0b1-48025e6a94cf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DefinedBenefitPlanInterestCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019e2c54-e84c-7236-9b29-32c6ed37b33e" xlink:to="loc_us-gaap_DefinedBenefitPlanInterestCost_019e2c54-e84c-7342-b0b1-48025e6a94cf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets_019e2c54-e84c-7ee5-836d-21708079a3cd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019e2c54-e84c-7236-9b29-32c6ed37b33e" xlink:to="loc_us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets_019e2c54-e84c-7ee5-836d-21708079a3cd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAmortizationOfGainsLosses_019e2c54-e84c-7141-9b86-52d41fca1c8a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DefinedBenefitPlanAmortizationOfGainsLosses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019e2c54-e84c-7236-9b29-32c6ed37b33e" xlink:to="loc_us-gaap_DefinedBenefitPlanAmortizationOfGainsLosses_019e2c54-e84c-7141-9b86-52d41fca1c8a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit_019e2c54-e84c-7a36-9e1b-373373b197ca" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019e2c54-e84c-7236-9b29-32c6ed37b33e" xlink:to="loc_us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit_019e2c54-e84c-7a36-9e1b-373373b197ca" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost_019e2c54-e84c-7c7b-83fe-799016dacd61" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019e2c54-e84c-7236-9b29-32c6ed37b33e" xlink:to="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost_019e2c54-e84c-7c7b-83fe-799016dacd61" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.unitedcontinentalholdings.com/role/PENSIONANDOTHERPOSTRETIREMENTBENEFITPLANSNarrativeDetails" xlink:type="simple" xlink:href="ual-20260630.xsd#PENSIONANDOTHERPOSTRETIREMENTBENEFITPLANSNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.unitedcontinentalholdings.com/role/PENSIONANDOTHERPOSTRETIREMENTBENEFITPLANSNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019e2c54-e84c-769e-bafd-4e87978e8e5c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_019e2c54-e84c-7cd3-8950-e868501db8da" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019e2c54-e84c-769e-bafd-4e87978e8e5c" xlink:to="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_019e2c54-e84c-7cd3-8950-e868501db8da" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeAxis_019e2c54-e84c-7298-bdb0-37f4c69f33de" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RetirementPlanTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_019e2c54-e84c-7cd3-8950-e868501db8da" xlink:to="loc_us-gaap_RetirementPlanTypeAxis_019e2c54-e84c-7298-bdb0-37f4c69f33de" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_019e2c54-e84c-7298-bdb0-37f4c69f33de_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_019e2c54-e84c-7298-bdb0-37f4c69f33de" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_019e2c54-e84c-7298-bdb0-37f4c69f33de_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_019e2c54-e84c-76f3-bee3-9b0325232191" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_019e2c54-e84c-7298-bdb0-37f4c69f33de" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_019e2c54-e84c-76f3-bee3-9b0325232191" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PensionPlansDefinedBenefitMember_019e2c54-e84c-7d4d-8be0-300b4081bbec" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PensionPlansDefinedBenefitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_019e2c54-e84c-76f3-bee3-9b0325232191" xlink:to="loc_us-gaap_PensionPlansDefinedBenefitMember_019e2c54-e84c-7d4d-8be0-300b4081bbec" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanContributionsByEmployer_019f60f5-1a07-76b6-90d7-9bf01e3a6c60" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DefinedBenefitPlanContributionsByEmployer"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019e2c54-e84c-769e-bafd-4e87978e8e5c" xlink:to="loc_us-gaap_DefinedBenefitPlanContributionsByEmployer_019f60f5-1a07-76b6-90d7-9bf01e3a6c60" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.unitedcontinentalholdings.com/role/FAIRVALUEMEASUREMENTSINVESTMENTSANDNOTESRECEIVABLEScheduleofFinancialAssetsandLiabilitiesMeasuredatFairValueonRecurringBasisDetails" xlink:type="simple" xlink:href="ual-20260630.xsd#FAIRVALUEMEASUREMENTSINVESTMENTSANDNOTESRECEIVABLEScheduleofFinancialAssetsandLiabilitiesMeasuredatFairValueonRecurringBasisDetails"/>
  <link:definitionLink xlink:role="http://www.unitedcontinentalholdings.com/role/FAIRVALUEMEASUREMENTSINVESTMENTSANDNOTESRECEIVABLEScheduleofFinancialAssetsandLiabilitiesMeasuredatFairValueonRecurringBasisDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e2c54-e84c-7e1a-9ae2-28e8264deb93" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e2c54-e84c-7bbc-a516-14f4905184a7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e2c54-e84c-7e1a-9ae2-28e8264deb93" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e2c54-e84c-7bbc-a516-14f4905184a7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019e2c54-e84c-7411-b755-de1b37506134" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e2c54-e84c-7bbc-a516-14f4905184a7" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019e2c54-e84c-7411-b755-de1b37506134" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_019e2c54-e84c-7411-b755-de1b37506134_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019e2c54-e84c-7411-b755-de1b37506134" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_019e2c54-e84c-7411-b755-de1b37506134_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_019e2c54-e84c-7653-87aa-7b4f8bb76f23" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019e2c54-e84c-7411-b755-de1b37506134" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_019e2c54-e84c-7653-87aa-7b4f8bb76f23" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_019e2c54-e84c-77ec-ab80-bbe85d32e52f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsRecurringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_019e2c54-e84c-7653-87aa-7b4f8bb76f23" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_019e2c54-e84c-77ec-ab80-bbe85d32e52f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e2c54-e84c-770c-99b2-8b05f7dbdeb1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e2c54-e84c-7bbc-a516-14f4905184a7" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e2c54-e84c-770c-99b2-8b05f7dbdeb1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e2c54-e84c-770c-99b2-8b05f7dbdeb1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e2c54-e84c-770c-99b2-8b05f7dbdeb1" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e2c54-e84c-770c-99b2-8b05f7dbdeb1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e2c54-e84c-7189-88bf-6fcb1992536e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e2c54-e84c-770c-99b2-8b05f7dbdeb1" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e2c54-e84c-7189-88bf-6fcb1992536e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_019e2c54-e84c-7a6c-8b73-e8cf0fca90cb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e2c54-e84c-7189-88bf-6fcb1992536e" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_019e2c54-e84c-7a6c-8b73-e8cf0fca90cb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_019e2c54-e84c-796e-8f6b-43bb3b27c5fc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e2c54-e84c-7189-88bf-6fcb1992536e" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_019e2c54-e84c-796e-8f6b-43bb3b27c5fc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_019e2c54-e84c-7b2b-9c37-b375eb9a239e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e2c54-e84c-7189-88bf-6fcb1992536e" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_019e2c54-e84c-7b2b-9c37-b375eb9a239e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeAxis_019e2c54-e84c-7fbf-a044-ad1889d1fcde" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e2c54-e84c-7bbc-a516-14f4905184a7" xlink:to="loc_us-gaap_InvestmentTypeAxis_019e2c54-e84c-7fbf-a044-ad1889d1fcde" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_019e2c54-e84c-7fbf-a044-ad1889d1fcde_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InvestmentTypeAxis_019e2c54-e84c-7fbf-a044-ad1889d1fcde" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_019e2c54-e84c-7fbf-a044-ad1889d1fcde_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_019e2c54-e84c-7ae9-96a9-0c7012056ff1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InvestmentTypeAxis_019e2c54-e84c-7fbf-a044-ad1889d1fcde" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_019e2c54-e84c-7ae9-96a9-0c7012056ff1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_019e2c54-e84c-77ad-afc9-fbfa08e860a2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_019e2c54-e84c-7ae9-96a9-0c7012056ff1" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_019e2c54-e84c-77ad-afc9-fbfa08e860a2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_019e2c54-e84c-71dd-9e55-4675285edfb2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_USGovernmentAgenciesDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_019e2c54-e84c-7ae9-96a9-0c7012056ff1" xlink:to="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_019e2c54-e84c-71dd-9e55-4675285edfb2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FixedIncomeSecuritiesMember_019e2c54-e84c-7093-a1e8-9a42b4b8dcd8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FixedIncomeSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_019e2c54-e84c-7ae9-96a9-0c7012056ff1" xlink:to="loc_us-gaap_FixedIncomeSecuritiesMember_019e2c54-e84c-7093-a1e8-9a42b4b8dcd8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_019e2c54-e84c-708d-92f7-85f168da3d88" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e2c54-e84c-7e1a-9ae2-28e8264deb93" xlink:to="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_019e2c54-e84c-708d-92f7-85f168da3d88" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_RestrictedCashNoncurrentFairValueDisclosure_019e2c54-e84c-7d56-997f-1d1ec7f4ebe2" xlink:href="ual-20260630.xsd#ual_RestrictedCashNoncurrentFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e2c54-e84c-7e1a-9ae2-28e8264deb93" xlink:to="loc_ual_RestrictedCashNoncurrentFairValueDisclosure_019e2c54-e84c-7d56-997f-1d1ec7f4ebe2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsFairValueDisclosure_019e2c54-e84c-761e-92fb-15008ea43270" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e2c54-e84c-7e1a-9ae2-28e8264deb93" xlink:to="loc_us-gaap_InvestmentsFairValueDisclosure_019e2c54-e84c-761e-92fb-15008ea43270" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesFvNi_019e2c54-e84c-7efb-a2c4-e8c03cc22693" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquitySecuritiesFvNi"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e2c54-e84c-7e1a-9ae2-28e8264deb93" xlink:to="loc_us-gaap_EquitySecuritiesFvNi_019e2c54-e84c-7efb-a2c4-e8c03cc22693" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.unitedcontinentalholdings.com/role/FAIRVALUEMEASUREMENTSINVESTMENTSANDNOTESRECEIVABLENarrativeDetails" xlink:type="simple" xlink:href="ual-20260630.xsd#FAIRVALUEMEASUREMENTSINVESTMENTSANDNOTESRECEIVABLENarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.unitedcontinentalholdings.com/role/FAIRVALUEMEASUREMENTSINVESTMENTSANDNOTESRECEIVABLENarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ual_FairValueLineItems_019e2c54-e84c-7d3f-b9dd-cf8cd9b27d49" xlink:href="ual-20260630.xsd#ual_FairValueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_FairValueTable_019e2c54-e84c-70cf-99f0-0db4c5db8fdb" xlink:href="ual-20260630.xsd#ual_FairValueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_ual_FairValueLineItems_019e2c54-e84c-7d3f-b9dd-cf8cd9b27d49" xlink:to="loc_ual_FairValueTable_019e2c54-e84c-70cf-99f0-0db4c5db8fdb" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByAssetClassAxis_019e2c54-e84c-739c-81ed-c9d4ec617404" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByAssetClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ual_FairValueTable_019e2c54-e84c-70cf-99f0-0db4c5db8fdb" xlink:to="loc_us-gaap_FairValueByAssetClassAxis_019e2c54-e84c-739c-81ed-c9d4ec617404" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019e2c54-e84c-739c-81ed-c9d4ec617404_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_019e2c54-e84c-739c-81ed-c9d4ec617404" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019e2c54-e84c-739c-81ed-c9d4ec617404_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019e2c54-e84c-74d5-9e60-0cbd33684363" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_019e2c54-e84c-739c-81ed-c9d4ec617404" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019e2c54-e84c-74d5-9e60-0cbd33684363" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_019e2c54-e84c-7507-b1da-a6c04feb07a6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019e2c54-e84c-74d5-9e60-0cbd33684363" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_019e2c54-e84c-7507-b1da-a6c04feb07a6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipAxis_019e2c54-e84c-7de8-a0b4-bcdf6858be94" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_OwnershipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ual_FairValueTable_019e2c54-e84c-70cf-99f0-0db4c5db8fdb" xlink:to="loc_srt_OwnershipAxis_019e2c54-e84c-7de8-a0b4-bcdf6858be94" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_019e2c54-e84c-7de8-a0b4-bcdf6858be94_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_OwnershipAxis_019e2c54-e84c-7de8-a0b4-bcdf6858be94" xlink:to="loc_srt_OwnershipDomain_019e2c54-e84c-7de8-a0b4-bcdf6858be94_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_019e2c54-e84c-72c7-8169-f40e746c5bd4" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_OwnershipAxis_019e2c54-e84c-7de8-a0b4-bcdf6858be94" xlink:to="loc_srt_OwnershipDomain_019e2c54-e84c-72c7-8169-f40e746c5bd4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_AzulLinhasAereasBrasileirasS.A.Member_019e2c54-e84c-7dd2-9a81-28e8386f99c6" xlink:href="ual-20260630.xsd#ual_AzulLinhasAereasBrasileirasS.A.Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_OwnershipDomain_019e2c54-e84c-72c7-8169-f40e746c5bd4" xlink:to="loc_ual_AzulLinhasAereasBrasileirasS.A.Member_019e2c54-e84c-7dd2-9a81-28e8386f99c6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019e2c54-e84c-7157-8bd6-7682261a1708" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ual_FairValueTable_019e2c54-e84c-70cf-99f0-0db4c5db8fdb" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019e2c54-e84c-7157-8bd6-7682261a1708" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_019e2c54-e84c-7157-8bd6-7682261a1708_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019e2c54-e84c-7157-8bd6-7682261a1708" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_019e2c54-e84c-7157-8bd6-7682261a1708_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_019e2c54-e84c-7ecb-828f-865e227918b0" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019e2c54-e84c-7157-8bd6-7682261a1708" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_019e2c54-e84c-7ecb-828f-865e227918b0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_AzulLinhasAereasBrasileirasS.A.Member_019e2c54-e84c-7b49-a900-1c3c6e39ffbd" xlink:href="ual-20260630.xsd#ual_AzulLinhasAereasBrasileirasS.A.Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019e2c54-e84c-7ecb-828f-865e227918b0" xlink:to="loc_ual_AzulLinhasAereasBrasileirasS.A.Member_019e2c54-e84c-7b49-a900-1c3c6e39ffbd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_RepublicAirwaysHoldingsIncMember_019e2c54-e84c-7ce0-8d1d-640167d3a71a" xlink:href="ual-20260630.xsd#ual_RepublicAirwaysHoldingsIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019e2c54-e84c-7ecb-828f-865e227918b0" xlink:to="loc_ual_RepublicAirwaysHoldingsIncMember_019e2c54-e84c-7ce0-8d1d-640167d3a71a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_CommuteAirLLCMember_019e2c54-e84c-773b-b732-2991fbabc1be" xlink:href="ual-20260630.xsd#ual_CommuteAirLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019e2c54-e84c-7ecb-828f-865e227918b0" xlink:to="loc_ual_CommuteAirLLCMember_019e2c54-e84c-773b-b732-2991fbabc1be" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_UnitedAirlinesVenturesSustainableFlightFundMember_019e2c54-e84c-7940-9f87-8638042524e4" xlink:href="ual-20260630.xsd#ual_UnitedAirlinesVenturesSustainableFlightFundMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019e2c54-e84c-7ecb-828f-865e227918b0" xlink:to="loc_ual_UnitedAirlinesVenturesSustainableFlightFundMember_019e2c54-e84c-7940-9f87-8638042524e4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_OtherEquityInvestmentsMember_019e2c54-e84c-7163-ab08-bd187942efc0" xlink:href="ual-20260630.xsd#ual_OtherEquityInvestmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019e2c54-e84c-7ecb-828f-865e227918b0" xlink:to="loc_ual_OtherEquityInvestmentsMember_019e2c54-e84c-7163-ab08-bd187942efc0" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019e2c54-e84c-7fa1-980d-40bb32e77920" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ual_FairValueTable_019e2c54-e84c-70cf-99f0-0db4c5db8fdb" xlink:to="loc_dei_LegalEntityAxis_019e2c54-e84c-7fa1-980d-40bb32e77920" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019e2c54-e84c-7fa1-980d-40bb32e77920_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019e2c54-e84c-7fa1-980d-40bb32e77920" xlink:to="loc_dei_EntityDomain_019e2c54-e84c-7fa1-980d-40bb32e77920_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019e2c54-e84c-7f74-b7d8-6e292596fe5e" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019e2c54-e84c-7fa1-980d-40bb32e77920" xlink:to="loc_dei_EntityDomain_019e2c54-e84c-7f74-b7d8-6e292596fe5e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_RepublicAirwaysHoldingsIncMember_019e2c54-e84c-7943-9dbd-bf4851a104ae" xlink:href="ual-20260630.xsd#ual_RepublicAirwaysHoldingsIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019e2c54-e84c-7f74-b7d8-6e292596fe5e" xlink:to="loc_ual_RepublicAirwaysHoldingsIncMember_019e2c54-e84c-7943-9dbd-bf4851a104ae" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_MesaAirlinesInc.Member_019e2c54-e84c-70d0-be49-5f576ddffc9a" xlink:href="ual-20260630.xsd#ual_MesaAirlinesInc.Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019e2c54-e84c-7f74-b7d8-6e292596fe5e" xlink:to="loc_ual_MesaAirlinesInc.Member_019e2c54-e84c-70d0-be49-5f576ddffc9a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_CommuteAirLLCMember_019e2c54-e84c-704e-990e-d5040cc10385" xlink:href="ual-20260630.xsd#ual_CommuteAirLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019e2c54-e84c-7f74-b7d8-6e292596fe5e" xlink:to="loc_ual_CommuteAirLLCMember_019e2c54-e84c-704e-990e-d5040cc10385" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_AvailableForSaleInvestmentsMaturityTerm_019e2c54-e84c-71db-9a11-fc7b639fb759" xlink:href="ual-20260630.xsd#ual_AvailableForSaleInvestmentsMaturityTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ual_FairValueLineItems_019e2c54-e84c-7d3f-b9dd-cf8cd9b27d49" xlink:to="loc_ual_AvailableForSaleInvestmentsMaturityTerm_019e2c54-e84c-71db-9a11-fc7b639fb759" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_EquitySecuritiesRestructuringAgreementCommittedInvestmentAmount_019e2c54-e84c-7e6f-9a0f-1cea5b5b97a5" xlink:href="ual-20260630.xsd#ual_EquitySecuritiesRestructuringAgreementCommittedInvestmentAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ual_FairValueLineItems_019e2c54-e84c-7d3f-b9dd-cf8cd9b27d49" xlink:to="loc_ual_EquitySecuritiesRestructuringAgreementCommittedInvestmentAmount_019e2c54-e84c-7e6f-9a0f-1cea5b5b97a5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_EquitySecuritiesRestructuringAgreementCommittedInvestmentShares_019e2c54-e84c-7b34-bf63-3ea3a3f8711e" xlink:href="ual-20260630.xsd#ual_EquitySecuritiesRestructuringAgreementCommittedInvestmentShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ual_FairValueLineItems_019e2c54-e84c-7d3f-b9dd-cf8cd9b27d49" xlink:to="loc_ual_EquitySecuritiesRestructuringAgreementCommittedInvestmentShares_019e2c54-e84c-7b34-bf63-3ea3a3f8711e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityOwnershipPercentageExcludingConsolidatedEntityAndEquityMethodInvestee_019e2c54-e84c-73b2-9e56-de42f117f116" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityOwnershipPercentageExcludingConsolidatedEntityAndEquityMethodInvestee"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ual_FairValueLineItems_019e2c54-e84c-7d3f-b9dd-cf8cd9b27d49" xlink:to="loc_us-gaap_EquityOwnershipPercentageExcludingConsolidatedEntityAndEquityMethodInvestee_019e2c54-e84c-73b2-9e56-de42f117f116" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestments_019e2c54-e84c-7728-9139-a8787bd95bea" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ual_FairValueLineItems_019e2c54-e84c-7d3f-b9dd-cf8cd9b27d49" xlink:to="loc_us-gaap_EquityMethodInvestments_019e2c54-e84c-7728-9139-a8787bd95bea" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_019e2c54-e84c-70f9-8a04-f59345c98198" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityMethodInvestmentOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ual_FairValueLineItems_019e2c54-e84c-7d3f-b9dd-cf8cd9b27d49" xlink:to="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_019e2c54-e84c-70f9-8a04-f59345c98198" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_EquityMethodInvestmentSharesReceivedForCommitmentConsideration_019e2c54-e84c-7d32-b2c8-b50cb4efe672" xlink:href="ual-20260630.xsd#ual_EquityMethodInvestmentSharesReceivedForCommitmentConsideration"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ual_FairValueLineItems_019e2c54-e84c-7d3f-b9dd-cf8cd9b27d49" xlink:to="loc_ual_EquityMethodInvestmentSharesReceivedForCommitmentConsideration_019e2c54-e84c-7d32-b2c8-b50cb4efe672" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_EquityMethodInvestmentAdditionalOwnershipPercentageReceivedForCommitmentConsideration_019e2c54-e84c-7d91-bc82-d93752caff01" xlink:href="ual-20260630.xsd#ual_EquityMethodInvestmentAdditionalOwnershipPercentageReceivedForCommitmentConsideration"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ual_FairValueLineItems_019e2c54-e84c-7d3f-b9dd-cf8cd9b27d49" xlink:to="loc_ual_EquityMethodInvestmentAdditionalOwnershipPercentageReceivedForCommitmentConsideration_019e2c54-e84c-7d91-bc82-d93752caff01" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfAircraftOperated_019e2c54-e84c-760a-8ea2-6bc43ecc8f3c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NumberOfAircraftOperated"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ual_FairValueLineItems_019e2c54-e84c-7d3f-b9dd-cf8cd9b27d49" xlink:to="loc_us-gaap_NumberOfAircraftOperated_019e2c54-e84c-760a-8ea2-6bc43ecc8f3c" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount_019e2c54-e84c-75e7-8ff0-b80c283fc489" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ual_FairValueLineItems_019e2c54-e84c-7d3f-b9dd-cf8cd9b27d49" xlink:to="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount_019e2c54-e84c-75e7-8ff0-b80c283fc489" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAfterAllowanceForCreditLoss_019e2c54-e84c-7dcf-a9ac-c555865feecf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestAfterAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ual_FairValueLineItems_019e2c54-e84c-7d3f-b9dd-cf8cd9b27d49" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAfterAllowanceForCreditLoss_019e2c54-e84c-7dcf-a9ac-c555865feecf" xlink:type="arc" order="10"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.unitedcontinentalholdings.com/role/FAIRVALUEMEASUREMENTSINVESTMENTSANDNOTESRECEIVABLEScheduleofCarryingValuesandEstimatedFairValuesofFinancialInstrumentsDetails" xlink:type="simple" xlink:href="ual-20260630.xsd#FAIRVALUEMEASUREMENTSINVESTMENTSANDNOTESRECEIVABLEScheduleofCarryingValuesandEstimatedFairValuesofFinancialInstrumentsDetails"/>
  <link:definitionLink xlink:role="http://www.unitedcontinentalholdings.com/role/FAIRVALUEMEASUREMENTSINVESTMENTSANDNOTESRECEIVABLEScheduleofCarryingValuesandEstimatedFairValuesofFinancialInstrumentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019e2c54-e84c-7d85-89f6-885b6bc534c2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByBalanceSheetGroupingTable_019e2c54-e84c-75d6-965f-ad6db0d4a3ea" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByBalanceSheetGroupingTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019e2c54-e84c-7d85-89f6-885b6bc534c2" xlink:to="loc_us-gaap_FairValueByBalanceSheetGroupingTable_019e2c54-e84c-75d6-965f-ad6db0d4a3ea" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementBasisAxis_019e2c54-e84c-7244-ad67-a945455ce121" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByMeasurementBasisAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_019e2c54-e84c-75d6-965f-ad6db0d4a3ea" xlink:to="loc_us-gaap_FairValueByMeasurementBasisAxis_019e2c54-e84c-7244-ad67-a945455ce121" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019e2c54-e84c-7244-ad67-a945455ce121_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_019e2c54-e84c-7244-ad67-a945455ce121" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019e2c54-e84c-7244-ad67-a945455ce121_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueDisclosureItemAmountsDomain_019e2c54-e84c-77a5-9ad2-d436bb825db3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueDisclosureItemAmountsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_019e2c54-e84c-7244-ad67-a945455ce121" xlink:to="loc_us-gaap_FairValueDisclosureItemAmountsDomain_019e2c54-e84c-77a5-9ad2-d436bb825db3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019e2c54-e84c-79b4-aafa-e2825ab935c0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_019e2c54-e84c-77a5-9ad2-d436bb825db3" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019e2c54-e84c-79b4-aafa-e2825ab935c0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_019e2c54-e84c-7f34-adc5-288f826e4375" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CarryingReportedAmountFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019e2c54-e84c-79b4-aafa-e2825ab935c0" xlink:to="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_019e2c54-e84c-7f34-adc5-288f826e4375" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_019e2c54-e84c-7294-bbc4-1d3428e0605e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EstimateOfFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019e2c54-e84c-79b4-aafa-e2825ab935c0" xlink:to="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_019e2c54-e84c-7294-bbc4-1d3428e0605e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e2c54-e84c-7eb2-a666-489a6941c85a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_019e2c54-e84c-75d6-965f-ad6db0d4a3ea" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e2c54-e84c-7eb2-a666-489a6941c85a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e2c54-e84c-7eb2-a666-489a6941c85a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e2c54-e84c-7eb2-a666-489a6941c85a" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e2c54-e84c-7eb2-a666-489a6941c85a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e2c54-e84c-792c-9665-11b4032bc76f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e2c54-e84c-7eb2-a666-489a6941c85a" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e2c54-e84c-792c-9665-11b4032bc76f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_019e2c54-e84c-72c3-9594-040a03edb3c6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e2c54-e84c-792c-9665-11b4032bc76f" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_019e2c54-e84c-72c3-9594-040a03edb3c6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_019e2c54-e84c-793c-9311-8a910293799b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e2c54-e84c-792c-9665-11b4032bc76f" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_019e2c54-e84c-793c-9311-8a910293799b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_019e2c54-e84c-7168-a022-dad16999da07" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e2c54-e84c-792c-9665-11b4032bc76f" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_019e2c54-e84c-7168-a022-dad16999da07" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_019e2c54-e84c-7abe-9cf1-ac726bb3ee91" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019e2c54-e84c-7d85-89f6-885b6bc534c2" xlink:to="loc_us-gaap_LongTermDebt_019e2c54-e84c-7abe-9cf1-ac726bb3ee91" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtFairValue_019e2c54-e84c-7684-892d-d599c2c30353" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019e2c54-e84c-7d85-89f6-885b6bc534c2" xlink:to="loc_us-gaap_LongTermDebtFairValue_019e2c54-e84c-7684-892d-d599c2c30353" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.unitedcontinentalholdings.com/role/DEBTNarrativeDetails" xlink:type="simple" xlink:href="ual-20260630.xsd#DEBTNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.unitedcontinentalholdings.com/role/DEBTNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_019e2c54-e84c-76ba-9479-925d68bf513e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_019e2c54-e84c-7ae0-a5be-723696935ecd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e2c54-e84c-76ba-9479-925d68bf513e" xlink:to="loc_us-gaap_DebtInstrumentTable_019e2c54-e84c-7ae0-a5be-723696935ecd" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019e2c54-e84c-7808-afc6-4f5ab7124980" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019e2c54-e84c-7ae0-a5be-723696935ecd" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019e2c54-e84c-7808-afc6-4f5ab7124980" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019e2c54-e84c-7808-afc6-4f5ab7124980_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019e2c54-e84c-7808-afc6-4f5ab7124980" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019e2c54-e84c-7808-afc6-4f5ab7124980_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019e2c54-e84c-7626-872a-57e2c80204d0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019e2c54-e84c-7808-afc6-4f5ab7124980" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019e2c54-e84c-7626-872a-57e2c80204d0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_019e2c54-e84c-70e2-a1a6-d9d641229412" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019e2c54-e84c-7626-872a-57e2c80204d0" xlink:to="loc_us-gaap_SecuredDebtMember_019e2c54-e84c-70e2-a1a6-d9d641229412" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotesMember_019e2c54-e84c-766d-a771-08e221d49e24" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019e2c54-e84c-7626-872a-57e2c80204d0" xlink:to="loc_us-gaap_SeniorNotesMember_019e2c54-e84c-766d-a771-08e221d49e24" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnsecuredDebtMember_019f60fb-b03c-75e3-bc31-6b2bf4539e40" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnsecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019e2c54-e84c-7626-872a-57e2c80204d0" xlink:to="loc_us-gaap_UnsecuredDebtMember_019f60fb-b03c-75e3-bc31-6b2bf4539e40" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_019e2c54-e84c-7541-a224-97a8333bc9b6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019e2c54-e84c-7ae0-a5be-723696935ecd" xlink:to="loc_us-gaap_CreditFacilityAxis_019e2c54-e84c-7541-a224-97a8333bc9b6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019e2c54-e84c-7541-a224-97a8333bc9b6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_019e2c54-e84c-7541-a224-97a8333bc9b6" xlink:to="loc_us-gaap_CreditFacilityDomain_019e2c54-e84c-7541-a224-97a8333bc9b6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019e2c54-e84c-7412-bc75-4991f7f8c667" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_019e2c54-e84c-7541-a224-97a8333bc9b6" xlink:to="loc_us-gaap_CreditFacilityDomain_019e2c54-e84c-7412-bc75-4991f7f8c667" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_019e2c54-e84c-78d2-a058-cdc09d32fefa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_019e2c54-e84c-7412-bc75-4991f7f8c667" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_019e2c54-e84c-78d2-a058-cdc09d32fefa" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019e2c54-e84c-7003-91fb-59aa2e6e4fe2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019e2c54-e84c-7ae0-a5be-723696935ecd" xlink:to="loc_us-gaap_DebtInstrumentAxis_019e2c54-e84c-7003-91fb-59aa2e6e4fe2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019e2c54-e84c-7003-91fb-59aa2e6e4fe2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019e2c54-e84c-7003-91fb-59aa2e6e4fe2" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019e2c54-e84c-7003-91fb-59aa2e6e4fe2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019e2c54-e84c-79d0-afd5-349573cc3f3c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019e2c54-e84c-7003-91fb-59aa2e6e4fe2" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019e2c54-e84c-79d0-afd5-349573cc3f3c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_A5.375NotesDue2031Member_019e2c54-e84c-72a6-afae-0d12fe477d4f" xlink:href="ual-20260630.xsd#ual_A5.375NotesDue2031Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019e2c54-e84c-79d0-afd5-349573cc3f3c" xlink:to="loc_ual_A5.375NotesDue2031Member_019e2c54-e84c-72a6-afae-0d12fe477d4f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_TermLoanDue2024Member_019e2c54-e84c-7a9c-9912-5e1720893d0e" xlink:href="ual-20260630.xsd#ual_TermLoanDue2024Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019e2c54-e84c-79d0-afd5-349573cc3f3c" xlink:to="loc_ual_TermLoanDue2024Member_019e2c54-e84c-7a9c-9912-5e1720893d0e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_A4.875NotesDue2029Member_019e2c54-e84c-79d7-a3b7-256c9c0f243c" xlink:href="ual-20260630.xsd#ual_A4.875NotesDue2029Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019e2c54-e84c-79d0-afd5-349573cc3f3c" xlink:to="loc_ual_A4.875NotesDue2029Member_019e2c54-e84c-79d7-a3b7-256c9c0f243c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_EquipmentNotesAircraftPurchaseFinancingMember_019f1c1a-1daf-7e80-8540-7c6d379199d6" xlink:href="ual-20260630.xsd#ual_EquipmentNotesAircraftPurchaseFinancingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019e2c54-e84c-79d0-afd5-349573cc3f3c" xlink:to="loc_ual_EquipmentNotesAircraftPurchaseFinancingMember_019f1c1a-1daf-7e80-8540-7c6d379199d6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_DebtFinancingAgreementsMember_019f49cb-befa-76da-8d7d-b62df853d87f" xlink:href="ual-20260630.xsd#ual_DebtFinancingAgreementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019e2c54-e84c-79d0-afd5-349573cc3f3c" xlink:to="loc_ual_DebtFinancingAgreementsMember_019f49cb-befa-76da-8d7d-b62df853d87f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_A4.375SecuredNotesDue2026Member_019e2c54-e84c-77d8-8b6a-1d1a9cebe0b8" xlink:href="ual-20260630.xsd#ual_A4.375SecuredNotesDue2026Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019e2c54-e84c-79d0-afd5-349573cc3f3c" xlink:to="loc_ual_A4.375SecuredNotesDue2026Member_019e2c54-e84c-77d8-8b6a-1d1a9cebe0b8" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_A4.625SecuredNotesDue2029Member_019e2c54-e84c-77ef-9953-ffd0a046d882" xlink:href="ual-20260630.xsd#ual_A4.625SecuredNotesDue2029Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019e2c54-e84c-79d0-afd5-349573cc3f3c" xlink:to="loc_ual_A4.625SecuredNotesDue2029Member_019e2c54-e84c-77ef-9953-ffd0a046d882" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_PayrollSupportProgramNotesDue2030Member_019f1c92-8e2e-7323-a1fc-e339d9ae3950" xlink:href="ual-20260630.xsd#ual_PayrollSupportProgramNotesDue2030Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019e2c54-e84c-79d0-afd5-349573cc3f3c" xlink:to="loc_ual_PayrollSupportProgramNotesDue2030Member_019f1c92-8e2e-7323-a1fc-e339d9ae3950" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_PayrollSupportProgramNote1Due2031Member_019f60fb-b03c-7cdc-b030-242a237e67ca" xlink:href="ual-20260630.xsd#ual_PayrollSupportProgramNote1Due2031Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019e2c54-e84c-79d0-afd5-349573cc3f3c" xlink:to="loc_ual_PayrollSupportProgramNote1Due2031Member_019f60fb-b03c-7cdc-b030-242a237e67ca" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_PayrollSupportProgramNote2Due2031Member_019f6c08-d483-71a1-8c26-78013b98b7e4" xlink:href="ual-20260630.xsd#ual_PayrollSupportProgramNote2Due2031Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019e2c54-e84c-79d0-afd5-349573cc3f3c" xlink:to="loc_ual_PayrollSupportProgramNote2Due2031Member_019f6c08-d483-71a1-8c26-78013b98b7e4" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_019e2c54-e84c-7f17-bdeb-f44b15f4d445" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentRedemptionPeriodAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019e2c54-e84c-7ae0-a5be-723696935ecd" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_019e2c54-e84c-7f17-bdeb-f44b15f4d445" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_019e2c54-e84c-7f17-bdeb-f44b15f4d445_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentRedemptionPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_019e2c54-e84c-7f17-bdeb-f44b15f4d445" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_019e2c54-e84c-7f17-bdeb-f44b15f4d445_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_019e2c54-e84c-71b8-862f-8a2e439870d6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentRedemptionPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_019e2c54-e84c-7f17-bdeb-f44b15f4d445" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_019e2c54-e84c-71b8-862f-8a2e439870d6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodOneMember_019e2c54-e84c-7423-b4d6-75aedd9b25f8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentRedemptionPeriodOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_019e2c54-e84c-71b8-862f-8a2e439870d6" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodOneMember_019e2c54-e84c-7423-b4d6-75aedd9b25f8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodTwoMember_019e2c54-e84c-7589-b891-881239739919" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentRedemptionPeriodTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_019e2c54-e84c-71b8-862f-8a2e439870d6" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodTwoMember_019e2c54-e84c-7589-b891-881239739919" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateAxis_019e2c54-e84c-797e-a5d9-bffb4dc32802" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VariableRateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019e2c54-e84c-7ae0-a5be-723696935ecd" xlink:to="loc_us-gaap_VariableRateAxis_019e2c54-e84c-797e-a5d9-bffb4dc32802" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_019e2c54-e84c-797e-a5d9-bffb4dc32802_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_019e2c54-e84c-797e-a5d9-bffb4dc32802" xlink:to="loc_us-gaap_VariableRateDomain_019e2c54-e84c-797e-a5d9-bffb4dc32802_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_019e2c54-e84c-7567-bd58-4fc0fc3542e0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_019e2c54-e84c-797e-a5d9-bffb4dc32802" xlink:to="loc_us-gaap_VariableRateDomain_019e2c54-e84c-7567-bd58-4fc0fc3542e0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredOvernightFinancingRateSofrMember_019e2c54-e84c-7214-ad77-47f5df1ef728" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SecuredOvernightFinancingRateSofrMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_019e2c54-e84c-7567-bd58-4fc0fc3542e0" xlink:to="loc_us-gaap_SecuredOvernightFinancingRateSofrMember_019e2c54-e84c-7214-ad77-47f5df1ef728" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_OtherMarketRatesMember_019e2c54-e84c-75e2-a6ca-cc0850af4ecd" xlink:href="ual-20260630.xsd#ual_OtherMarketRatesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_019e2c54-e84c-7567-bd58-4fc0fc3542e0" xlink:to="loc_ual_OtherMarketRatesMember_019e2c54-e84c-75e2-a6ca-cc0850af4ecd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019f1c1a-1daf-72c0-803c-4ded52b048f5" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019e2c54-e84c-7ae0-a5be-723696935ecd" xlink:to="loc_srt_RangeAxis_019f1c1a-1daf-72c0-803c-4ded52b048f5" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019f1c1a-1daf-72c0-803c-4ded52b048f5_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019f1c1a-1daf-72c0-803c-4ded52b048f5" xlink:to="loc_srt_RangeMember_019f1c1a-1daf-72c0-803c-4ded52b048f5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019f1c1a-1daf-7a22-a893-1ce625bd5880" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019f1c1a-1daf-72c0-803c-4ded52b048f5" xlink:to="loc_srt_RangeMember_019f1c1a-1daf-7a22-a893-1ce625bd5880" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_WeightedAverageMember_019f49b1-40a8-7332-b574-3ef584633774" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_WeightedAverageMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019f1c1a-1daf-7a22-a893-1ce625bd5880" xlink:to="loc_srt_WeightedAverageMember_019f49b1-40a8-7332-b574-3ef584633774" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_019e2c54-e84c-7d3e-aaea-c9f8c3038f22" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e2c54-e84c-76ba-9479-925d68bf513e" xlink:to="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_019e2c54-e84c-7d3e-aaea-c9f8c3038f22" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_019e2c54-e84c-7e83-b967-7302cb61f7fc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e2c54-e84c-76ba-9479-925d68bf513e" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_019e2c54-e84c-7e83-b967-7302cb61f7fc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_019e2c54-e84c-7a47-9da7-97bc2d5398e5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e2c54-e84c-76ba-9479-925d68bf513e" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_019e2c54-e84c-7a47-9da7-97bc2d5398e5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019e2c54-e84c-70a0-8ce0-cdc629a0b647" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e2c54-e84c-76ba-9479-925d68bf513e" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019e2c54-e84c-70a0-8ce0-cdc629a0b647" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_DebtInstrumentIssuePricePercentageOfPrincipal_019e2c54-e84c-73c9-b819-2d5142788ae6" xlink:href="ual-20260630.xsd#ual_DebtInstrumentIssuePricePercentageOfPrincipal"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e2c54-e84c-76ba-9479-925d68bf513e" xlink:to="loc_ual_DebtInstrumentIssuePricePercentageOfPrincipal_019e2c54-e84c-73c9-b819-2d5142788ae6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPricePercentage_019e2c54-e84c-7002-a9d1-d4b715f1c11c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentRedemptionPricePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e2c54-e84c-76ba-9479-925d68bf513e" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPricePercentage_019e2c54-e84c-7002-a9d1-d4b715f1c11c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_019e2c54-e84c-7ecf-8dfa-6f1932b2414d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e2c54-e84c-76ba-9479-925d68bf513e" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_019e2c54-e84c-7ecf-8dfa-6f1932b2414d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfDebt_019f1c1a-1daf-79b8-96e8-04c13804044b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromIssuanceOfDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e2c54-e84c-76ba-9479-925d68bf513e" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfDebt_019f1c1a-1daf-79b8-96e8-04c13804044b" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitment_019f60d2-c0ec-7328-b491-0e465b7d25d5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherCommitment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e2c54-e84c-76ba-9479-925d68bf513e" xlink:to="loc_us-gaap_OtherCommitment_019f60d2-c0ec-7328-b491-0e465b7d25d5" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfDebt_019f1c92-8e2e-7468-9291-9bc7fc242e99" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RepaymentsOfDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e2c54-e84c-76ba-9479-925d68bf513e" xlink:to="loc_us-gaap_RepaymentsOfDebt_019f1c92-8e2e-7468-9291-9bc7fc242e99" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRepurchasedFaceAmount_019e2c54-e84c-7e5f-8aed-92051dfb14b8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentRepurchasedFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e2c54-e84c-76ba-9479-925d68bf513e" xlink:to="loc_us-gaap_DebtInstrumentRepurchasedFaceAmount_019e2c54-e84c-7e5f-8aed-92051dfb14b8" xlink:type="arc" order="10"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.unitedcontinentalholdings.com/role/DEBTScheduleofContractualPrincipalPaymentsDetails" xlink:type="simple" xlink:href="ual-20260630.xsd#DEBTScheduleofContractualPrincipalPaymentsDetails"/>
  <link:definitionLink xlink:role="http://www.unitedcontinentalholdings.com/role/DEBTScheduleofContractualPrincipalPaymentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_019e2c54-e84c-7e78-bde4-77448e39c099" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_019e2c54-e84c-7861-a416-4056fa92473f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e2c54-e84c-7e78-bde4-77448e39c099" xlink:to="loc_us-gaap_DebtInstrumentTable_019e2c54-e84c-7861-a416-4056fa92473f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019e2c54-e84c-75f7-99c0-8bb5e86b49e0" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019e2c54-e84c-7861-a416-4056fa92473f" xlink:to="loc_dei_LegalEntityAxis_019e2c54-e84c-75f7-99c0-8bb5e86b49e0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019e2c54-e84c-75f7-99c0-8bb5e86b49e0_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019e2c54-e84c-75f7-99c0-8bb5e86b49e0" xlink:to="loc_dei_EntityDomain_019e2c54-e84c-75f7-99c0-8bb5e86b49e0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019e2c54-e84c-7de7-b4f1-4ae0ea83a394" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019e2c54-e84c-75f7-99c0-8bb5e86b49e0" xlink:to="loc_dei_EntityDomain_019e2c54-e84c-7de7-b4f1-4ae0ea83a394" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_UalAndUnitedMember_019e2c54-e84c-7a67-9eb7-ab1878eb233e" xlink:href="ual-20260630.xsd#ual_UalAndUnitedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019e2c54-e84c-7de7-b4f1-4ae0ea83a394" xlink:to="loc_ual_UalAndUnitedMember_019e2c54-e84c-7a67-9eb7-ab1878eb233e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear_019e2c54-e84c-7056-bbfa-ae73a3b3301a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e2c54-e84c-7e78-bde4-77448e39c099" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear_019e2c54-e84c-7056-bbfa-ae73a3b3301a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths_019e2c54-e84c-7ce3-b1bd-681c7624b568" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e2c54-e84c-7e78-bde4-77448e39c099" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths_019e2c54-e84c-7ce3-b1bd-681c7624b568" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo_019e2c54-e84c-71dc-9b1e-6357907328aa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e2c54-e84c-7e78-bde4-77448e39c099" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo_019e2c54-e84c-71dc-9b1e-6357907328aa" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree_019e2c54-e84c-7248-9cad-04721fabb496" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e2c54-e84c-7e78-bde4-77448e39c099" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree_019e2c54-e84c-7248-9cad-04721fabb496" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour_019e2c54-e84c-7828-8d09-023a4097f905" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e2c54-e84c-7e78-bde4-77448e39c099" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour_019e2c54-e84c-7828-8d09-023a4097f905" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_LongTermDebtMaturityAfterYearFour_019e2c54-e84c-7876-8c8c-9d0fa17ac545" xlink:href="ual-20260630.xsd#ual_LongTermDebtMaturityAfterYearFour"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e2c54-e84c-7e78-bde4-77448e39c099" xlink:to="loc_ual_LongTermDebtMaturityAfterYearFour_019e2c54-e84c-7876-8c8c-9d0fa17ac545" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_019e2c54-e84c-7847-a86d-e003f011e599" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e2c54-e84c-7e78-bde4-77448e39c099" xlink:to="loc_us-gaap_LongTermDebt_019e2c54-e84c-7847-a86d-e003f011e599" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.unitedcontinentalholdings.com/role/COMMITMENTSANDCONTINGENCIESScheduleofEstimatedFuturePaymentsofContractualObligationDetails" xlink:type="simple" xlink:href="ual-20260630.xsd#COMMITMENTSANDCONTINGENCIESScheduleofEstimatedFuturePaymentsofContractualObligationDetails"/>
  <link:definitionLink xlink:role="http://www.unitedcontinentalholdings.com/role/COMMITMENTSANDCONTINGENCIESScheduleofEstimatedFuturePaymentsofContractualObligationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationLineItems_019e2c54-e84c-7bb1-bd36-9b08b14d04dd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnrecordedUnconditionalPurchaseObligationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationTable_019e2c54-e84c-78f1-a90e-8b4ef9eeba43" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnrecordedUnconditionalPurchaseObligationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationLineItems_019e2c54-e84c-7bb1-bd36-9b08b14d04dd" xlink:to="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationTable_019e2c54-e84c-78f1-a90e-8b4ef9eeba43" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis_019e2c54-e84c-72fd-8e17-1b8335888dec" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationTable_019e2c54-e84c-78f1-a90e-8b4ef9eeba43" xlink:to="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis_019e2c54-e84c-72fd-8e17-1b8335888dec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnconditionalPurchaseObligationCategoryOfGoodsOrServicesAcquiredDomain_019e2c54-e84c-72fd-8e17-1b8335888dec_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnconditionalPurchaseObligationCategoryOfGoodsOrServicesAcquiredDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis_019e2c54-e84c-72fd-8e17-1b8335888dec" xlink:to="loc_us-gaap_UnconditionalPurchaseObligationCategoryOfGoodsOrServicesAcquiredDomain_019e2c54-e84c-72fd-8e17-1b8335888dec_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnconditionalPurchaseObligationCategoryOfGoodsOrServicesAcquiredDomain_019e2c54-e84c-7bdc-909d-55a5d0b014ab" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnconditionalPurchaseObligationCategoryOfGoodsOrServicesAcquiredDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis_019e2c54-e84c-72fd-8e17-1b8335888dec" xlink:to="loc_us-gaap_UnconditionalPurchaseObligationCategoryOfGoodsOrServicesAcquiredDomain_019e2c54-e84c-7bdc-909d-55a5d0b014ab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AirlineCapacityPurchaseArrangementsMember_019e2c54-e84c-771a-b852-98938a428d86" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AirlineCapacityPurchaseArrangementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnconditionalPurchaseObligationCategoryOfGoodsOrServicesAcquiredDomain_019e2c54-e84c-7bdc-909d-55a5d0b014ab" xlink:to="loc_us-gaap_AirlineCapacityPurchaseArrangementsMember_019e2c54-e84c-771a-b852-98938a428d86" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationDueInRemainderOfFiscalYear_019e2c54-e84c-77b6-a8df-a5a769abfd78" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnrecordedUnconditionalPurchaseObligationDueInRemainderOfFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationLineItems_019e2c54-e84c-7bb1-bd36-9b08b14d04dd" xlink:to="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationDueInRemainderOfFiscalYear_019e2c54-e84c-77b6-a8df-a5a769abfd78" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnFirstAnniversary_019e2c54-e84c-7304-822d-7d59b7d22925" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnFirstAnniversary"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationLineItems_019e2c54-e84c-7bb1-bd36-9b08b14d04dd" xlink:to="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnFirstAnniversary_019e2c54-e84c-7304-822d-7d59b7d22925" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnSecondAnniversary_019e2c54-e84c-751b-8304-e1215e164c44" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnSecondAnniversary"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationLineItems_019e2c54-e84c-7bb1-bd36-9b08b14d04dd" xlink:to="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnSecondAnniversary_019e2c54-e84c-751b-8304-e1215e164c44" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnThirdAnniversary_019e2c54-e84c-7dc3-968e-225fa6253b93" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnThirdAnniversary"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationLineItems_019e2c54-e84c-7bb1-bd36-9b08b14d04dd" xlink:to="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnThirdAnniversary_019e2c54-e84c-7dc3-968e-225fa6253b93" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnFourthAnniversary_019e2c54-e84c-7f73-883a-aeaebcd3802d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnFourthAnniversary"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationLineItems_019e2c54-e84c-7bb1-bd36-9b08b14d04dd" xlink:to="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnFourthAnniversary_019e2c54-e84c-7f73-883a-aeaebcd3802d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_UnrecordedUnconditionalPurchaseObligationToBePaidAfterYearFour_019e2c54-e84c-7769-bcfa-8aec77e85110" xlink:href="ual-20260630.xsd#ual_UnrecordedUnconditionalPurchaseObligationToBePaidAfterYearFour"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationLineItems_019e2c54-e84c-7bb1-bd36-9b08b14d04dd" xlink:to="loc_ual_UnrecordedUnconditionalPurchaseObligationToBePaidAfterYearFour_019e2c54-e84c-7769-bcfa-8aec77e85110" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceSheetAmount_019e2c54-e84c-72ae-8ffd-06604a560f15" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceSheetAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationLineItems_019e2c54-e84c-7bb1-bd36-9b08b14d04dd" xlink:to="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceSheetAmount_019e2c54-e84c-72ae-8ffd-06604a560f15" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.unitedcontinentalholdings.com/role/COMMITMENTSANDCONTINGENCIESNarrativeDetails" xlink:type="simple" xlink:href="ual-20260630.xsd#COMMITMENTSANDCONTINGENCIESNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.unitedcontinentalholdings.com/role/COMMITMENTSANDCONTINGENCIESNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ual_CommitmentsAndContingenciesLineItems_019e2c54-e84c-727f-ac5f-5c9454df4f02" xlink:href="ual-20260630.xsd#ual_CommitmentsAndContingenciesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_CommitmentsAndContingenciesTable_019e2c54-e84c-70f4-a25c-cef7ba1dbc3e" xlink:href="ual-20260630.xsd#ual_CommitmentsAndContingenciesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_ual_CommitmentsAndContingenciesLineItems_019e2c54-e84c-727f-ac5f-5c9454df4f02" xlink:to="loc_ual_CommitmentsAndContingenciesTable_019e2c54-e84c-70f4-a25c-cef7ba1dbc3e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019e2c54-e84c-7430-b03e-44c47c2b5a98" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ual_CommitmentsAndContingenciesTable_019e2c54-e84c-70f4-a25c-cef7ba1dbc3e" xlink:to="loc_us-gaap_DebtInstrumentAxis_019e2c54-e84c-7430-b03e-44c47c2b5a98" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019e2c54-e84c-7430-b03e-44c47c2b5a98_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019e2c54-e84c-7430-b03e-44c47c2b5a98" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019e2c54-e84c-7430-b03e-44c47c2b5a98_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019e2c54-e84c-773b-bd83-b237cb025cbf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019e2c54-e84c-7430-b03e-44c47c2b5a98" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019e2c54-e84c-773b-bd83-b237cb025cbf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_FloatingRateDebtMember_019e2c54-e84c-7bb4-8754-5a0c54a031fd" xlink:href="ual-20260630.xsd#ual_FloatingRateDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019e2c54-e84c-773b-bd83-b237cb025cbf" xlink:to="loc_ual_FloatingRateDebtMember_019e2c54-e84c-7bb4-8754-5a0c54a031fd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_LoansAndLeasesFromNonUSEntitiesMember_019e2c54-e84c-75db-971c-de6d19f73dcd" xlink:href="ual-20260630.xsd#ual_LoansAndLeasesFromNonUSEntitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019e2c54-e84c-773b-bd83-b237cb025cbf" xlink:to="loc_ual_LoansAndLeasesFromNonUSEntitiesMember_019e2c54-e84c-75db-971c-de6d19f73dcd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019e2c54-e84c-73c3-a5e7-c55ecee765b0" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ual_CommitmentsAndContingenciesTable_019e2c54-e84c-70f4-a25c-cef7ba1dbc3e" xlink:to="loc_dei_LegalEntityAxis_019e2c54-e84c-73c3-a5e7-c55ecee765b0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019e2c54-e84c-73c3-a5e7-c55ecee765b0_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019e2c54-e84c-73c3-a5e7-c55ecee765b0" xlink:to="loc_dei_EntityDomain_019e2c54-e84c-73c3-a5e7-c55ecee765b0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019e2c54-e84c-7abb-b738-d1babbeca4cc" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019e2c54-e84c-73c3-a5e7-c55ecee765b0" xlink:to="loc_dei_EntityDomain_019e2c54-e84c-7abb-b738-d1babbeca4cc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_UnitedAirLinesIncMember_019e2c54-e84c-7a66-8efc-1e58047b6aeb" xlink:href="ual-20260630.xsd#ual_UnitedAirLinesIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019e2c54-e84c-7abb-b738-d1babbeca4cc" xlink:to="loc_ual_UnitedAirLinesIncMember_019e2c54-e84c-7a66-8efc-1e58047b6aeb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_019f4d78-b2fc-72c7-a05a-ff8efba9ac42" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ual_CommitmentsAndContingenciesTable_019e2c54-e84c-70f4-a25c-cef7ba1dbc3e" xlink:to="loc_srt_CounterpartyNameAxis_019f4d78-b2fc-72c7-a05a-ff8efba9ac42" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019f4d78-b2fc-72c7-a05a-ff8efba9ac42_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_019f4d78-b2fc-72c7-a05a-ff8efba9ac42" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019f4d78-b2fc-72c7-a05a-ff8efba9ac42_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019f4d78-b2fc-77dd-a372-1714572a0655" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_019f4d78-b2fc-72c7-a05a-ff8efba9ac42" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019f4d78-b2fc-77dd-a372-1714572a0655" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_AssociationOfFlightAttendantsMember_019f4d79-16e6-7099-b9bb-19855ab253b4" xlink:href="ual-20260630.xsd#ual_AssociationOfFlightAttendantsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019f4d78-b2fc-77dd-a372-1714572a0655" xlink:to="loc_ual_AssociationOfFlightAttendantsMember_019f4d79-16e6-7099-b9bb-19855ab253b4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_019e2c54-e84c-7d9b-9a94-12e1c7740124" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ual_CommitmentsAndContingenciesLineItems_019e2c54-e84c-727f-ac5f-5c9454df4f02" xlink:to="loc_us-gaap_LongTermDebt_019e2c54-e84c-7d9b-9a94-12e1c7740124" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_DebtInstrumentRemainingTerm_019e2c54-e84c-7d20-a89b-dace77b30fd4" xlink:href="ual-20260630.xsd#ual_DebtInstrumentRemainingTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ual_CommitmentsAndContingenciesLineItems_019e2c54-e84c-727f-ac5f-5c9454df4f02" xlink:to="loc_ual_DebtInstrumentRemainingTerm_019e2c54-e84c-7d20-a89b-dace77b30fd4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractualObligation_019e2c54-e84c-7d1a-b8d1-2da2f20c8ffc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ContractualObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ual_CommitmentsAndContingenciesLineItems_019e2c54-e84c-727f-ac5f-5c9454df4f02" xlink:to="loc_us-gaap_ContractualObligation_019e2c54-e84c-7d1a-b8d1-2da2f20c8ffc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityNumberOfEmployees_019e2c54-e84c-7bda-a416-97ec52de49bd" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityNumberOfEmployees"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ual_CommitmentsAndContingenciesLineItems_019e2c54-e84c-727f-ac5f-5c9454df4f02" xlink:to="loc_dei_EntityNumberOfEmployees_019e2c54-e84c-7bda-a416-97ec52de49bd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_PercentageOfEmployeesRepresentedByLaborOrganizations_019e2c54-e84c-79e1-bb81-d5a92bfbf42f" xlink:href="ual-20260630.xsd#ual_PercentageOfEmployeesRepresentedByLaborOrganizations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ual_CommitmentsAndContingenciesLineItems_019e2c54-e84c-727f-ac5f-5c9454df4f02" xlink:to="loc_ual_PercentageOfEmployeesRepresentedByLaborOrganizations_019e2c54-e84c-79e1-bb81-d5a92bfbf42f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_LaborContractRatificationBonus_019e2c54-e84c-7754-88e3-a387a1c3c63e" xlink:href="ual-20260630.xsd#ual_LaborContractRatificationBonus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ual_CommitmentsAndContingenciesLineItems_019e2c54-e84c-727f-ac5f-5c9454df4f02" xlink:to="loc_ual_LaborContractRatificationBonus_019e2c54-e84c-7754-88e3-a387a1c3c63e" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://xbrl.sec.gov/ecd/role/IndividualsOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2026/ecd-2026.xsd#IndividualsOnly"/>
  <link:definitionLink xlink:role="http://xbrl.sec.gov/ecd/role/IndividualsOnly" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AllIndividualsMember" xlink:href="https://xbrl.sec.gov/ecd/2026/ecd-2026.xsd#ecd_AllIndividualsMember"/>
    <link:loc xlink:type="locator" xlink:label="loc_ual_MichaelLeskinenMember_019f4d82-2297-7d1f-9704-646394b83ed1" xlink:href="ual-20260630.xsd#ual_MichaelLeskinenMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllIndividualsMember" xlink:to="loc_ual_MichaelLeskinenMember_019f4d82-2297-7d1f-9704-646394b83ed1" xlink:type="arc" order="2"/>
  </link:definitionLink>
</link:linkbase>
