New Accounting Pronouncements and Changes in Accounting Principles [Abstract] New Accounting Pronouncements or Change in Accounting Principle [Table] New Accounting Pronouncements or Change in Accounting Principle [Table] Adjustments for New Accounting Pronouncements [Axis] Adjustments for New Accounting Pronouncements [Axis] Type of Adoption [Domain] Type of Adoption [Domain] ASU 2016-13 Accounting Standards Update 2016-13 [Member] New Accounting Pronouncements or Change in Accounting Principle [Line Items] New Accounting Pronouncements or Change in Accounting Principle [Line Items] Cumulative-effect adjustment to retained earnings Cumulative Effect of New Accounting Principle in Period of Adoption Statement of Financial Position [Abstract] Statement [Table] Statement [Table] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] United Airlines, Inc. United Air Lines Inc [Member] United Airlines, Inc. [Member] Statement [Line Items] Statement [Line Items] Allowance for credit losses Accounts Receivable, Allowance for Credit Loss, Current Obsolescence allowance for aircraft fuel, spare parts and supplies Airline Related Inventory, Valuation Reserves Accumulated amortization on intangibles Finite-Lived Intangible Assets, Accumulated Amortization Allowance for credit losses on notes receivable Financing Receivable, Allowance for Credit Loss Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Common shares, authorized (in shares) Common Stock, Shares Authorized Common shares, issued (in shares) Common Stock, Shares, Issued Common shares, outstanding (in shares) Common Stock, Shares, Outstanding Other Income and Expenses [Abstract] Impairment of assets Asset Impairment Charges Severance and benefit costs Postemployment Benefits, Period Expense (Gains) losses on sale of assets and other special charges Gain (Loss) On Sale Of Other Assets And Other Miscellaneous Charges Amount of gain (loss) on sale of other assets and other miscellaneous charges. Total operating special charges Restructuring, Settlement and Impairment Provisions Nonoperating credit loss on BRW Term Loan and related guarantee Financing Receivable, Credit Loss, Expense (Reversal) Nonoperating unrealized (gains) losses on investments Gain (Loss) On Financial Instruments, Non-Operating Gain (Loss) On Financial Instruments, Non-Operating Total special charges, credit losses and unrealized (gains) losses on investments, net Special Charges And Losses On Financial Instruments, Non-Operating, Before Tax Special Charges And Losses On Financial Instruments, Nonoperating, Before Tax Income tax benefit, net of valuation allowance Income Tax Expense (Benefit) Special Charges Income tax expense (benefit) special charges. Total special charges, credit losses and unrealized (gains) losses on investments, net of income taxes Special Items Net of Income Tax Benefit(s) Total special items in the period. Income Tax Disclosure [Abstract] Effective income tax rate Effective Income Tax Rate Reconciliation, Percent Valuation allowance Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount Revenue from Contract with Customer [Abstract] REVENUE Revenue from Contract with Customer [Text Block] Unusual or Infrequent Items, or Both [Abstract] COMBINED NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS (UNAUDITED) Unusual or Infrequent Items, or Both, Disclosure [Text Block] Cover [Abstract] Entities [Table] Entities [Table] Entity Information [Line Items] Entity Information [Line Items] Document Type Document Type Document Fiscal Period Focus Document Fiscal Period Focus Document Quarterly Report Document Quarterly Report Document Period End Date Document Period End Date Document Transition Report Document Transition Report Amendment Flag Amendment Flag Document Fiscal Year Focus Document Fiscal Year Focus Current Fiscal Year End Date Current Fiscal Year End Date Entity File Number Entity File Number Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Entity Tax Identification Number Entity Tax Identification Number Entity Address, Address Line One Entity Address, Address Line One Entity Address, City or Town Entity Address, City or Town Entity Address, State or Province Entity Address, State or Province Entity Address, Postal Zip Code Entity Address, Postal Zip Code City Area Code City Area Code Local Phone Number Local Phone Number Entity Current Reporting Status Entity Current Reporting Status Entity Interactive Data Current Entity Interactive Data Current Entity Filer Category Entity Filer Category Entity Small Business Entity Small Business Entity Emerging Growth Company Entity Emerging Growth Company Entity Shell Company Entity Shell Company Title of 12(b) Security Title of 12(b) Security Trading Symbol Trading Symbol Security Exchange Name Security Exchange Name Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Commitments and Contingencies Disclosure [Abstract] Last nine months of 2020 Unrecorded Unconditional Purchase Obligation, Due in Remainder of Fiscal Year 2021 Unrecorded Unconditional Purchase Obligation, Due within Two Years 2022 Unrecorded Unconditional Purchase Obligation, Due within Three Years 2023 Unrecorded Unconditional Purchase Obligation, Due within Four Years 2024 Unrecorded Unconditional Purchase Obligation, Due within Five Years After 2024 Unrecorded Unconditional Purchase Obligation, Due after Five Years Total commitments Unrecorded Unconditional Purchase Obligation Fair Value Disclosures [Abstract] Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Level 1 Fair Value, Inputs, Level 1 [Member] Level 2 Fair Value, Inputs, Level 2 [Member] Level 3 Fair Value, Inputs, Level 3 [Member] Measurement Basis [Axis] Measurement Basis [Axis] Fair Value Measurement [Domain] Fair Value Measurement [Domain] Portion at Fair Value Measurement Portion at Fair Value Measurement [Member] Carrying Amount Reported Value Measurement [Member] Fair Value Estimate of Fair Value Measurement [Member] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Long-term debt Long-term Debt Long-term debt Long-term Debt, Fair Value Recently Issued Accounting Standards New Accounting Pronouncements, Policy [Policy Text Block] Fair Value of Financial Instruments Fair Value of Financial Instruments, Policy [Policy Text Block] Revenue From Contract With Customer [Table] Revenue From Contract With Customer [Table] Revenue From Contract With Customer [Table] [Table] Product and Service [Axis] Product and Service [Axis] Product and Service [Domain] Product and Service [Domain] Advance Ticket Sales Advance Ticket Sales [Member] Advance Ticket Sales [Member] Ancillary Fees Passenger - Ancillary Fees [Member] Passenger - Ancillary Fees [Member] Other Operating Revenue Product and Service, Other [Member] Collaborative Arrangement and Arrangement Other than Collaborative [Axis] Collaborative Arrangement and Arrangement Other than Collaborative [Axis] Collaborative Arrangement and Arrangement Other than Collaborative [Domain] Collaborative Arrangement and Arrangement Other than Collaborative [Domain] Chase and Other Partner Agreements Chase And Other Partner Agreements [Member] Chase And Other Partner Agreements [Member] Revenue From Contract With Customer [Line Items] Revenue From Contract With Customer [Line Items] [Line Items] for Revenue From Contract With Customer [Table] [Table] Expiration period for electronic travel certificates Electronic Travel Certificates, Expiration Period Electronic Travel Certificates, Expiration Period Revenue recognized Contract with Customer, Liability, Revenue Recognized Operating revenue Revenue from Contract with Customer, Excluding Assessed Tax Earnings Per Share [Abstract] Schedule of Stock by Class [Table] Schedule of Stock by Class [Table] Sale of Stock [Axis] Sale of Stock [Axis] Sale of Stock [Domain] Sale of Stock [Domain] Public Offering Public Offering [Member] Public Offering [Member] Over-Allotment Option Over-Allotment Option [Member] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent Event Subsequent Event [Member] Class of Stock [Line Items] Class of Stock [Line Items] Number of shares issued (in shares) Stock Issued During Period, Shares, New Issues Par value of common stock (in dollars per share) Sale price (in dollars per share) Shares Issued, Price Per Share Over-allotment option period Sale Of Stock, Over-Allotment Option Period Sale Of Stock, Over-Allotment Option Period Equity [Abstract] ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) Comprehensive Income (Loss) Note [Text Block] Income Statement [Abstract] Passenger revenue Passenger [Member] Cargo Cargo and Freight [Member] Other operating revenue Operating revenue: Revenues [Abstract] Operating expense: Costs and Expenses [Abstract] Salaries and related costs Labor and Related Expense Aircraft fuel Fuel Costs Regional capacity purchase Airline, Capacity Purchase Arrangements Landing fees and other rent Landing Fees and Other Rentals Depreciation and amortization Depreciation, Depletion and Amortization, Nonproduction Aircraft maintenance materials and outside repairs Aircraft Maintenance, Materials, and Repairs Distribution expenses Selling Expense Aircraft rent Aircraft Rental Special charges Other operating expenses Other Cost and Expense, Operating Total operating expenses Costs and Expenses Operating income (loss) Operating Income (Loss) Nonoperating income (expense): Nonoperating Income (Expense) [Abstract] Interest expense Interest Costs Incurred Interest capitalized Interest Costs Capitalized Adjustment Interest income Investment Income, Interest Unrealized gains (losses) on investments, net Unrealized Gain (Loss) on Investments Miscellaneous, net Other Nonoperating Income (Expense) Total nonoperating expense, net Nonoperating Income (Expense) Income (loss) before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Income tax expense (benefit) Income Tax Expense (Benefit) Net income (loss) Net Income (Loss) Attributable to Parent Earnings (loss) per share, basic and diluted (in dollars per share) Earnings Per Share, Basic and Diluted Long-term Purchase Commitment [Table] Long-term Purchase Commitment [Table] Aircraft Type [Axis] Aircraft Type [Axis] Aircraft [Domain] Aircraft [Domain] Airbus A321XLR Airbus A321XLR [Member] Airbus A321XLR [Member] Airbus A350 Airbus A350 [Member] Airbus A350 [Member] Boeing 737 MAX Boeing 737 Max [Member] Boeing 737 Max Boeing 787 Boeing 787 [Member] Boeing 787. Embraer E175 Embraer E175 [Member] Embraer E175 [Member] Long-term Purchase Commitment [Line Items] Long-term Purchase Commitment [Line Items] Number of firm commitments Unrecorded Unconditional Purchase Obligation, Minimum Quantity Required Scheduled Aircraft Deliveries Number Of Aircrafts Expected To Take Delivery [Abstract] Number Of Aircrafts Expected To Take Delivery [Abstract] Last Nine Months of 2020 Number Of Aircrafts Expected To Take Delivery, Remainder Of Year Number Of Aircrafts Expected To Take Delivery, Remainder Of Year 2021 Number Of Aircrafts Expected To Take Delivery, Year Two Number Of Aircrafts Expected To Take Delivery, Year Two After 2021 Number Of Aircrafts Expected To Take Delivery, Thereafter Number Of Aircrafts Expected To Take Delivery, Thereafter Last Nine Months of 2020 (if order is lifted) Number Of Aircrafts Expected To Take Delivery If Order Is Lifted, Remainder Of Year Number Of Aircrafts Expected To Take Delivery If Order Is Lifted, Remainder Of Year 2021 (if order is lifted) Number Of Aircrafts Expected To Take Delivery If Order Is Lifted, Year Two Number Of Aircrafts Expected To Take Delivery If Order Is Lifted, Year Two Statement of Cash Flows [Abstract] Reconciliation of cash, cash equivalents and restricted cash: Cash and Cash Equivalents [Abstract] Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Restricted cash Restricted Cash and Cash Equivalents, Noncurrent Total cash, cash equivalents and restricted cash Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents COMMITMENTS AND CONTINGENCIES Commitments and Contingencies Disclosure [Text Block] Receivables [Abstract] Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Counterparty Name [Axis] Counterparty Name [Axis] Counterparty Name [Domain] Counterparty Name [Domain] BRW BRW Aviation Holding LLC And BRW Aviation LLC (“BRW”) [Member] BRW Aviation Holding LLC and BRW Aviation LLC (“BRW”) [Member] Class of Financing Receivable [Axis] Class of Financing Receivable [Axis] Class of Financing Receivable [Domain] Class of Financing Receivable [Domain] Term Loan Receivable Term Loan Receivable [Member] Term Loan Receivable [Member] Accounts, Notes, Loans and Financing Receivable [Line Items] Accounts, Notes, Loans and Financing Receivable [Line Items] Loan amount Financing Receivable, Face Amount Financing Receivable, Face Amount Number of shares pledged as collateral (in shares) Financing Receivable, Agreement, Shares Pledged As Collateral Financing Receivable, Agreement, Shares Pledged As Collateral Implied value equivalent of shares pledged as collateral (in ADRs) Financing Receivable, Agreement, Shares Pledged As Collateral, Implied Value Equivalent, American Depository Receipts Financing Receivable, Agreement, Shares Pledged As Collateral, American Depository Receipts Carrying amount of loan receivable Financing Receivable, after Allowance for Credit Loss Debt Disclosure [Abstract] Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Pass-Through Certificates Pass-Through Certificates [Member] Pass-Through Certificates [Member] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Class AA Pass-Through Certificates Issued September 2019 Class AA Pass-Through Certificates Issued September 2019 [Member] Class AA Pass-Through Certificates Issued September 2019 [Member] Class A Pass-Through Certificates Issued September 2019 Class A Pass-Through Certificates Issued September 2019 [Member] Class A Pass-Through Certificates Issued September 2019 [Member] Class B Pass-Through Certificates Issued September 2019 Class B Pass-Through Certificates Issued September 2019 [Member] Class B Pass-Through Certificates Issued September 2019 [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Face Amount Debt Instrument, Face Amount Stated interest rate Debt Instrument, Interest Rate, Stated Percentage Total proceeds received from issuance of debt Proceeds from Issuance of Long-term Debt Total debt recorded Long-term Debt, Gross DEBT Long-term Debt [Text Block] BRW Term Loan Loans, Notes, Trade and Other Receivables Disclosure [Text Block] Financial Assets and Liabilities Measured at Fair Value on Recurring Basis Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Carrying Values and Estimated Fair Values of Financial Instruments Fair Value, by Balance Sheet Grouping [Table Text Block] Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Frequent Flyer Frequent Flyer Program [Member] Frequent Flyer Program [Member] Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Frequent Flyer Deferred Revenue [Roll Forward] Movement In Contract With Customer Liability [Roll Forward] Movement In Contract With Customer Liability [Roll Forward] Total Frequent flyer deferred revenue - beginning balance Contract with Customer, Liability Total miles awarded Frequent Flyer Mileage Miles Awarded in Period Frequent flyer mileage miles awarded in period. Travel miles redeemed (Passenger revenue) Travel Miles Redemption, Frequent Flyer Deferred Revenue Travel miles redemption, frequent flyer deferred revenue. Non-travel miles redeemed (Other operating revenue) Non-Travel Miles Redemption, Frequent Flyer Deferred Revenue Non-travel miles redemption, frequent flyer deferred revenue. Total Frequent flyer deferred revenue - ending balance Employee-related Liabilities [Abstract] Share-based compensation expense Share-based Payment Arrangement, Expense Unrecognized share-based compensation Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount UAL And United UAL And United [Member] UAL And United [Member] Last nine months of 2020 Long-term Debt, Maturities, Repayments of Principal, Remainder of Fiscal Year 2021 Long-term Debt, Maturities, Repayments of Principal in Year Two 2022 Long-term Debt, Maturities, Repayments of Principal in Year Three 2023 Long-term Debt, Maturities, Repayments of Principal in Year Four 2024 Long-term Debt, Maturities, Repayments of Principal in Year Five After 2024 Long-term Debt, Maturities, Repayments of Principal after Year Five Long-term debt Components of Accumulated Other Comprehensive Income, Net of Tax Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Computation of Basic and Diluted Earnings Per Share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] EARNINGS (LOSS) PER SHARE Earnings Per Share [Text Block] Credit Facility [Axis] Credit Facility [Axis] Credit Facility [Domain] Credit Facility [Domain] Revolving Credit Facility Revolving Credit Facility [Member] Used Aircraft Facility Used Aircraft Facility [Member] Used Aircraft Facility Spare Parts Facility Spare Parts Facility [Member] Spare Parts Facility Spare Engines Facility Spare Engines Credit Agreement [Member] Spare Engines Credit Agreement PSP Note Payroll Support Program (PSP) Note [Member] Payroll Support Program (PSP) Note [Member] Debt Instrument, Interest Rate Period [Axis] Debt Instrument, Interest Rate Period [Axis] Debt Instrument, Interest Rate Period [Axis] Debt Instrument, Interest Rate Period [Domain] Debt Instrument, Interest Rate Period [Domain] [Domain] for Debt Instrument, Interest Rate Period [Axis] Before 180 Days Debt Instrument, Interest Rate Period, 1-179 Days [Member] Debt Instrument, Interest Rate Period, 1-179 Days [Member] 90-180 Days Debt Instrument, Interest Rate Period, 1-89 Days [Member] Debt Instrument, Interest Rate Period, 1-89 Days [Member] Before 90 Days Debt Instrument, Interest Rate Period, 90-179 Days [Member] Debt Instrument, Interest Rate Period, 90-179 Days [Member] 180-270 Days Debt Instrument, Interest Rate Period, 180-269 Days [Member] Debt Instrument, Interest Rate Period, 180-269 Days [Member] 270 Days and Longer Debt Instrument, Interest Rate Period, 270 Days And Longer [Member] Debt Instrument, Interest Rate Period, 270 Days And Longer [Member] Years 1 through 5 Debt Instrument, Interest Rate Period, Years 1 Through 5 [Member] Debt Instrument, Interest Rate Period, Years 1 Through 5 [Member] Years 6 through 10 Debt Instrument, Interest Rate Period, Years 6 Through 10 [Member] Debt Instrument, Interest Rate Period, Years 6 Through 10 [Member] Secured Debt Secured Debt [Member] Unsecured Debt Unsecured Debt [Member] Variable Rate [Axis] Variable Rate [Axis] Variable Rate [Domain] Variable Rate [Domain] LIBOR London Interbank Offered Rate (LIBOR) [Member] Alternative Rate Alternative Rate [Member] Alternative Rate [Member] SOFR Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member] Available under revolving credit facility Line of Credit Facility, Remaining Borrowing Capacity Face amount Interest rate floor Debt Instrument, Variable Rate Floor Debt Instrument, Variable Rate Floor Percent spread on variable rate Debt Instrument, Basis Spread on Variable Rate Minimum required unrestricted cash and cash equivalents and unused commitments available Debt Instrument, Covenant, Minimum Required Unrestricted Cash And Cash Equivalents And Unused Commitments Debt Instrument, Covenant, Minimum Required Unrestricted Cash And Cash Equivalents And Unused Commitments Minimum required ratio of appraised value of collateral to the outstanding obligations Debt Instrument, Covenant, Ratio Of Collateral To Outstanding Obligations, Minimum Debt Instrument, Covenant, Ratio Of Collateral To Outstanding Obligations, Minimum Minimum required ratio of appraised value of collateral to the outstanding obligations if certain spare parts are used Debt Instrument, Covenant, Ratio Of Collateral To Outstanding Obligations, Conditional Minimum Debt Instrument, Covenant, Ratio Of Collateral To Outstanding Obligations, Conditional Minimum Total funding provided under the Payroll Support Program Payroll Support Program, Funding Provided Payroll Support Program, Total Funding Provided Percent increase in the principal amount based on any disbursement made by the U.S. Treasury Department Debt Instrument, Percentage Increase In Face Amount Upon Disbursements Debt Instrument, Percentage Increase In Face Amount Upon Disbursements Aggregate principal amount after all disbursements Debt Instrument, Face Amount After All Disbursements Debt Instrument, Face Amount After All Disbursements Term of debt Debt Instrument, Term Fair Value [Table] Fair Value [Table] Fair Value [Table] Investment, Name [Axis] Investment, Name [Axis] Investment, Name [Domain] Investment, Name [Domain] Azul Azul [Member] Azul [Member] Asset Class [Axis] Asset Class [Axis] Asset Class [Domain] Asset Class [Domain] Asset-Backed Securities Asset-backed Securities [Member] Corporate Debt Corporate Debt Securities [Member] CDARS Certificates of Deposit [Member] U.S. Government and Agency Notes Us Government Agencies Debt Securities and Other Fixed Income Securities [Member] Us Government Agencies Debt Securities and Other Fixed Income Securities [Member] Other Fixed-Income Securities Fixed Income Securities [Member] Financial Instrument [Axis] Financial Instrument [Axis] Financial Instruments [Domain] Financial Instruments [Domain] Preferred Stock Preferred Stock [Member] Statistical Measurement [Axis] Statistical Measurement [Axis] Statistical Measurement [Domain] Statistical Measurement [Domain] Minimum Minimum [Member] Maximum Maximum [Member] Fair Value [Line Items] Fair Value [Line Items] Fair Value [Line Items] Available-for-sale securities remaining maturities Available for Sale Investment Maturity Term Available for Sale Investment Maturity Term Equity stake in Azul Equity Securities, Ownership Percentage Equity Securities, Ownership Percentage Gain (loss) on equity securities Equity Securities, FV-NI, Unrealized Gain (Loss) Carrying value of investment Equity Securities, FV-NI Unrealized gain (loss) on derivative asset Unrealized Gain (Loss) on Derivatives Fair Value, Recurring and Nonrecurring [Table] Fair Value, Recurring and Nonrecurring [Table] Investment Type [Axis] Investment Type [Axis] Investments [Domain] Investments [Domain] Corporate debt Asset-backed securities U.S. government and agency notes US Government Agencies Debt Securities [Member] Certificates of deposit placed through an account registry service (CDARS) Other fixed-income securities Other investments measured at net asset value (NAV) Other Investments Measured At Net Asset Value [Member] Other Investments Measured At Net Asset Value [Member] Measurement Frequency [Axis] Measurement Frequency [Axis] Measurement Frequency [Domain] Measurement Frequency [Domain] Measured on a Recurring Basis Fair Value, Recurring [Member] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Cash and cash equivalents Cash and Cash Equivalents, Fair Value Disclosure Short-term investments Investments, Fair Value Disclosure Restricted cash Restricted Cash, Fair Value Disclosure Restricted Cash Fair Value Disclosure Equity securities AVH Derivative Assets Derivative Asset Other assets Other Long-term Investments FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS Fair Value Disclosures [Text Block] Components of Special Charges Restructuring and Related Costs [Table Text Block] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Award Type Award Type [Axis] Award Type [Domain] Award Type [Domain] RSUs Restricted Stock Units (RSUs) [Member] Time-Vested RSUs Time-Vested Restricted Stock Units (RSUs) [Member] Time-Vested Restricted Stock Units (RSUs) [Member] Performance-Based RSUs Performance-Based Restricted Stock Units (RSUs) [Member] Performance-Based Restricted Stock Units (RSUs) [Member] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Compensation and Retirement Disclosure [Abstract] Retirement Benefits [Abstract] Awards granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Vesting period Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Number of days used to compute performance period average closing price of restricted stock units Determination Period Average Closing Price The time period over which the stock closing prices are averaged to arrive at a per-share valuation for equity based awards such as Restricted Stock Units, Performance Share and other equity based awards. Components of Net Periodic Benefit Cost Schedule of Net Benefit Costs [Table Text Block] Information Related to Share-Based Compensation Share-based Payment Arrangement, Cost by Plan [Table Text Block] Statement of Stockholders' Equity [Abstract] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Common Stock Common Stock [Member] Additional Capital Invested Additional Paid-in Capital [Member] Treasury Stock Treasury Stock [Member] Retained Earnings Retained Earnings [Member] Accumulated Other Comprehensive Income (Loss) AOCI Attributable to Parent [Member] Receivable from Related Parties, Net Receivables from Stockholder [Member] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Balance (in shares) Balance Stockholders' Equity Attributable to Parent Net income (loss) Other comprehensive income (loss) Other Comprehensive Income (Loss), Net of Tax Dividend to UAL Capital Contributions To Parent Capital Contributions To Parent Stock settled share-based compensation APIC, Share-based Payment Arrangement, Increase for Cost Recognition Repurchases of common stock (in shares) Treasury Stock, Shares, Acquired Repurchases of common stock Treasury Stock, Value, Acquired, Cost Method Net treasury stock issued for share-based awards (in shares) Shares Issued, Shares, Share-based Payment Arrangement, after Forfeiture Net treasury stock issued for share-based awards Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture Adoption of new accounting standard Other Stockholders' Equity, Other Balance (in shares) Balance INCOME TAXES Income Tax Disclosure [Text Block] Schedule of Defined Benefit Plans Disclosures [Table] Schedule of Defined Benefit Plans Disclosures [Table] Retirement Plan Type [Axis] Retirement Plan Type [Axis] Retirement Plan Type [Domain] Retirement Plan Type [Domain] Pension Benefits Pension Plan [Member] Other Postretirement Benefits Other Postretirement Benefits Plan [Member] Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Disclosure [Line Items] Service cost Defined Benefit Plan, Service Cost Interest cost Defined Benefit Plan, Interest Cost Expected return on plan assets Defined Benefit Plan, Expected Return (Loss) on Plan Assets Amortization of unrecognized (gain) loss Defined Benefit Plan, Amortization of Gain (Loss) Amortization of prior service credit Defined Benefit Plan, Amortization of Prior Service Cost (Credit) Settlement loss Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement Total Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Earnings (loss) available to common stockholders Net Income (Loss) Available to Common Stockholders, Basic Basic weighted-average shares outstanding (in shares) Weighted Average Number of Shares Outstanding, Basic Effect of employee stock awards (in shares) Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Diluted weighted-average shares outstanding (in shares) Weighted Average Number of Shares Outstanding, Diluted Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Antidilutive Securities [Axis] Antidilutive Securities [Axis] Antidilutive Securities, Name [Domain] Antidilutive Securities, Name [Domain] Employee Stock Awards Share-based Payment Arrangement [Member] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Securities excluded from the computation of the diluted per share amount (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount RECENTLY ISSUED ACCOUNTING STANDARDS New Accounting Pronouncements and Changes in Accounting Principles [Text Block] Details of Pass Through Trusts Schedule of Debt Instruments Pass Through Trusts [Table Text Block] Schedule of Debt Instruments Pass Through Trusts Contractual Principal Payments under Long-Term Debt Agreements Schedule of Maturities of Long-term Debt [Table Text Block] Operating Revenue by Geographic Region Disaggregation of Revenue [Table Text Block] Roll Forward of Frequent Flyer Deferred Revenue Contract with Customer, Asset and Liability [Table Text Block] Commitments and Contingencies [Table] Commitments and Contingencies [Table] Commitments And Contingencies [Table] Airbus A319 Airbus A319s [Member] Airbus A319s [Member] Boeing 737-700 Boeing 737-700 [Member] Boeing 737-700 [Member] Tax-Exempt Special Facilities Revenue Bonds Tax Exempt Bonds [Member] Tax Exempt Bonds [Member] Aircraft Mortgage Debt Aircraft Mortgage Debt [Member] Aircraft Mortgage Debt [Member] Floating Rate Debt Floating Rate Debt [Member] Floating Rate Debt [Member] Loans and Leases from Non-U.S. Entities Loans And Leases From Non U S Entities [Member] Loans And Leases From Non U.S Entities [Member] Kingsland Kingsland Holdings Limited [Member] Kingsland Holdings Limited [Member] Commitments and Contingencies [Line Items] Commitments and Contingencies [Line Items] Commitments And Contingencies [Line Items] Number of aircraft committed to purchase Number of aircraft no longer expected to be assigned Number Of Aircraft No Longer Expected To Be Assigned Number Of Aircraft No Longer Expected To Be Assigned Number of aircraft purchase options exercised Number Of Aircraft Purchase Options Exercised Number Of Aircraft Purchase Options Exercised Number of aircraft subject to purchase rights assignment agreement Number Of Aircraft Subject To Purchase Rights Assignment Agreement Number Of Aircraft Subject To Purchase Rights Assignment Agreement Aggregate principal amount of guarantee Guarantor Obligations, Maximum Exposure, Undiscounted Number of shares that may be put to United (in shares) Loans Receivable, Agreement, Put Options Loans Receivable, Agreement, Put Options Number of ADRs that may be put into United (in shares) Loans Receivable, Agreement, Put Option, Deposit Receipts Loans Receivable, Agreement, Put Option, Deposit Receipts Market price of common stock at fifth anniversary (in dollars per share) Loans Receivable, Guarantee And Payout Share Price At Fifth Anniversary Loans Receivable, Guarantee And Payout Share Price At Fifth Anniversary Aggregate maximum possible combined put payment and guarantee amount Loans Receivable, Aggregate Maximum Payment And Guarantee Amount Loans Receivable, Aggregate Maximum Payment And Guarantee Amount Liability for the fair value of guarantees Guarantor Obligations, Current Carrying Value Additional expense recorded for guarantee Guarantor Obligations, Expense Guarantor Obligations, Expense Debt Remaining term of debt Debt Instrument Remaining Terms Years remaining on debt instruments. Aggregate balance Contractual Obligation Number of employees Entity Number of Employees Percentage of employees represented by various U.S. labor organizations Percentage Of Employees Represented By Labor Organizations Percentage of employees represented by labor organizations Schedule of Restructuring and Related Costs [Table] Schedule of Restructuring and Related Costs [Table] Indefinite-lived Intangible Assets [Axis] Indefinite-lived Intangible Assets [Axis] Indefinite-lived Intangible Assets, Major Class Name [Domain] Indefinite-lived Intangible Assets, Major Class Name [Domain] Routes Use Rights [Member] Restructuring Type [Axis] Restructuring Type [Axis] Type of Restructuring [Domain] Type of Restructuring [Domain] Transition of Fleet Types within Other Regional Carrier Contracts Fleet Transition Within Regional Carrier Contracts [Member] Fleet Transition Within Regional Carrier Contracts [Member] Voluntary Early-Out Program Voluntary Early Out Program [Member] Voluntary Early Out Program [Member] Trans States Airlines Trans States Airlines [Member] Trans States Airlines [Member] International Brotherhood of Teamsters International Brotherhood Of Teamsters [Member] International Brotherhood of Teamsters. Title of Individual [Axis] Title of Individual [Axis] Title of Individual [Domain] Title of Individual [Domain] Management Management [Member] Restructuring Cost and Reserve [Line Items] Restructuring Cost and Reserve [Line Items] Fair value of indefinite-lived intangible assets Indefinite-lived Intangible Assets (Excluding Goodwill) Impairment of intangible assets Impairment of Intangible Assets (Excluding Goodwill) Special charge related to wind-down Special charges Restructuring Charges Nonoperating unrealized losses on investments Gain (loss) for the change in fair value of equity investments Loss recorded for the change in fair value of certain derivative assets Derivative, Loss on Derivative Fair value adjustment for aircraft purchased off lease Special Charges, Fair Value Adjustment, Write-Offs, And Impairments Of Aircraft Special Charges, Fair Value Adjustment, Write-Offs, And Impairments Of Aircraft Gain for the change in fair value of certain derivative assets Derivative, Gain on Derivative Firm Commitments and Options to Purchase Aircraft and Summary of Commitments Long-term Purchase Commitment [Table Text Block] Statement of Comprehensive Income [Abstract] Other comprehensive income (loss), net of tax: Other Comprehensive Income (Loss), Net of Tax [Abstract] Employee benefit plans Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax Investments and other Other Comprehensive Income, Investments and Other, Net of Tax Other Comprehensive Income, Investments and Other, Net of Tax Total other comprehensive income (loss), net of tax Total comprehensive income (loss), net Comprehensive Income (Loss), Net of Tax, Attributable to Parent Cash Flows from Operating Activities: Net Cash Provided by (Used in) Operating Activities [Abstract] Net cash provided (used) by operating activities Net Cash Provided by (Used in) Operating Activities Cash Flows from Investing Activities: Net Cash Provided by (Used in) Investing Activities [Abstract] Capital expenditures Payments to Acquire Productive Assets Purchases of short-term and other investments Payments to Acquire Short-term Investments Proceeds from sale of short-term and other investments Proceeds from Sale, Maturity and Collection of Investments Other, net Payments for (Proceeds from) Other Investing Activities Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities Cash Flows from Financing Activities: Net Cash Provided by (Used in) Financing Activities [Abstract] Proceeds from issuance of short-term debt Proceeds from Short-term Debt Proceeds from issuance of long-term debt Payments of long-term debt Repayments of Long-term Debt Dividend to UAL Payments Of Dividends To Parent Company Payments of dividends to parent company. Repurchases of common stock Payments for Repurchase of Common Stock Principal payments under finance leases Finance Lease, Principal Payments Capitalized financing costs Payments of Debt Issuance Costs Other, net Proceeds from (Payments for) Other Financing Activities Net cash provided (used) in financing activities Net Cash Provided by (Used in) Financing Activities Net increase in cash, cash equivalents and restricted cash Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Cash, cash equivalents and restricted cash at beginning of the period Cash, cash equivalents and restricted cash at end of the period Investing and Financing Activities Not Affecting Cash: Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Property and equipment acquired through the issuance of debt Noncash or Part Noncash Acquisition, Fixed Assets Acquired Lease modifications and lease conversions Finance Lease, Conversion From Operating Lease, Recorded Property, Plant, And Equipment Finance Lease, Conversion From Operating Lease, Recorded Property, Plant, And Equipment Right-of-use assets acquired through operating leases Right-of-Use Asset Obtained in Exchange for Operating Lease Liability Property and equipment acquired through finance leases Right-of-Use Asset Obtained in Exchange for Finance Lease Liability Airline Destinations [Axis] Airline Destinations [Axis] Airline Destination [Domain] Airline Destination [Domain] Domestic (U.S. and Canada) Domestic Destination [Member] Atlantic Atlantic Destination [Member] Pacific Pacific Destination [Member] Latin America Latin America Destination [Member] Unusual or Infrequent Item, or Both [Table] Unusual or Infrequent Item, or Both [Table] CEO and President Chief Executive Officer [Member] Officers Officer [Member] Non-Employee Directors Director [Member] Class of Warrant or Right [Axis] Class of Warrant or Right [Axis] Class of Warrant or Right [Domain] Class of Warrant or Right [Domain] Initial Issuance Initial Warrant Issuance [Member] Initial Warrant Issuance [Member] Scenario [Axis] Scenario [Axis] Scenario [Domain] Scenario [Domain] Forecast Forecast [Member] Unusual or Infrequent Item, or Both [Line Items] Unusual or Infrequent Item, or Both [Line Items] Percent of capacity cut Unusual Or Infrequent Items, Percent Of Capacity Cut Unusual Or Infrequent Items, Percent Of Capacity Cut Rolling cancellation period Unusual Or Infrequent Items, Rolling Flight Cancellation Period Unusual Or Infrequent Items, Rolling Flight Cancellation Period Proceeds from issuance of secured term loans Proceeds from Issuance of Secured Debt Proceeds from the issuance of common stock Proceeds from Issuance of Common Stock Voluntary pay reduction Executive And Director Compensation, Voluntary Decrease In Salary, Percent Executive And Director Compensation, Voluntary Decrease In Salary, Percent Funding provided through loans under the Payroll Support Program Payroll Support Program, Funding Provided, Amounts Received Through Loans Payroll Support Program, Funding Provided, Amounts Received Through Loans Funding provided through direct grants under the Payroll Support Program Payroll Support Program, Funding Provided, Amounts Received Through Direct Grants Payroll Support Program, Funding Provided, Amounts Received Through Direct Grants Number of securities called by warrants (in shares) Class of Warrant or Right, Number of Securities Called by Warrants or Rights Warrant exercise price (in dollars per share) Class of Warrant or Right, Exercise Price of Warrants or Rights Warrant term Warrants and Rights Outstanding, Term Support funding received Proceeds From Federal Grants And Loans Proceeds From Federal Grants And Loans Expected borrowings Proceeds From Issuance Of Long-Term Debt, Expected Expected Proceeds From Issuance Of Long-Term Debt Expected term of debt Debt Instrument, Expected Term Debt Instrument, Expected Term Expected number of securities called by warrants (in shares) Class Of Warrant Or Right, Number Of Securities Called By Warrants Or Rights, Expected Class Of Warrant Or Right, Number Of Securities Called By Warrants Or Rights, Expected Expected exercise price of warrants (in dollars per share) Class Of Warrant Or Right, Exercise Price Of Warrants Or Rights, Expected Class Of Warrant Or Right, Exercise Price Of Warrants Or Rights, Expected ASSETS Assets [Abstract] Current assets: Assets, Current [Abstract] Short-term investments Short-term Investments Receivables, less allowance for credit losses (2020 — $30; 2019 — $9) Receivables, Net, Current Aircraft fuel, spare parts and supplies, less obsolescence allowance (2020 — $446; 2019 — $425) Airline Related Inventory, Net Prepaid expenses and other Prepaid Expense and Other Assets, Current Total current assets Assets, Current Operating property and equipment: Property, Plant and Equipment, Net [Abstract] Flight equipment Flight Equipment, Gross Other property and equipment Property, Plant and Equipment, Other, Gross Purchase deposits for flight equipment Deposits on Flight Equipment Total operating property and equipment Property, Plant, And Equipment And Finance Lease Right-Of-Use Asset, Before Accumulated Depreciation And Amortization Property, Plant, And Equipment And Finance Lease Right-Of-Use Asset, Before Accumulated Depreciation And Amortization Less — Accumulated depreciation and amortization Property, Plant, And Equipment And Finance Lease Right-Of-Use Asset, Accumulated Depreciation And Amortization Property, Plant, And Equipment And Finance Lease Right-Of-Use Asset, Accumulated Depreciation And Amortization Total operating property and equipment, net Property, Plant, And Equipment And Finance Lease Right-Of-Use Asset, After Accumulated Depreciation And Amortization Property, Plant, And Equipment And Finance Lease Right-Of-Use Asset, After Accumulated Depreciation And Amortization Operating lease right-of-use assets Operating Lease, Right-of-Use Asset Other assets: Other Assets, Noncurrent [Abstract] Goodwill Goodwill Intangibles, less accumulated amortization (2020 — $1,454; 2019 — $1,440) Intangible Assets, Net (Excluding Goodwill) Notes receivable, less allowance for credit losses (2020 — $549) Financing Receivable, after Allowance for Credit Loss, Noncurrent Investments in affiliates and other, net Investments and Other Noncurrent Assets Total other assets Other Assets, Noncurrent Total assets Assets LIABILITIES AND STOCKHOLDERS' EQUITY Liabilities and Equity [Abstract] Current liabilities: Liabilities, Current [Abstract] Advance ticket sales Contract With Customer, Liability, Current, Advance Ticket Sales Contract With Customer, Liability, Current, Advance Ticket Sales Accounts payable Accounts Payable, Current Frequent flyer deferred revenue Contract With Customer, Liability, Current, Frequent Flyer Contract With Customer, Liability, Current, Frequent Flyer Accrued salaries and benefits Employee-related Liabilities, Current Current maturities of long-term debt Long-term Debt, Current Maturities Current maturities of finance leases Finance Lease, Liability, Current Current maturities of operating leases Operating Lease, Liability, Current Other Other Liabilities, Current Total current liabilities Liabilities, Current Long-term debt Long-term Debt, Excluding Current Maturities Long-term obligations under finance leases Finance Lease, Liability, Noncurrent Long-term obligations under operating leases Operating Lease, Liability, Noncurrent Other liabilities and deferred credits: Deferred Credits and Other Liabilities [Abstract] Frequent flyer deferred revenue Contract With Customer, Liability, Noncurrent, Frequent Flyer Contract With Customer, Liability, Noncurrent, Frequent Flyer Postretirement benefit liability Liability, Other Postretirement Defined Benefit Plan, Noncurrent Pension liability Liability, Defined Benefit Pension Plan, Noncurrent Deferred income taxes Deferred Income Tax Liabilities, Net Other Other Liabilities, Noncurrent Total other liabilities and deferred credits Other Liabilities And Deferred Credits, Noncurrent Other Liabilities And Deferred Credits, Noncurrent Commitments and contingencies Commitments and Contingencies Stockholders' equity: Stockholders' Equity Attributable to Parent [Abstract] Preferred stock Preferred Stock, Value, Issued Common stock at par, $0.01 par value; authorized 1,000,000,000 shares; outstanding 247,256,855 and 251,216,381 shares at March 31, 2020 and December 31, 2019, respectively Common Stock, Value, Issued Additional capital invested Additional Paid in Capital, Common Stock Retained earnings Retained Earnings (Accumulated Deficit) Stock held in treasury, at cost Treasury Stock, Value Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Net of Tax Receivable from related parties Receivable from Shareholders or Affiliates for Issuance of Capital Stock Total stockholders' equity Total liabilities and stockholders' equity Liabilities and Equity SPECIAL CHARGES Restructuring and Related Activities Disclosure [Text Block] Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income (Loss) [Table] Pension and Other Postretirement Liabilities Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] Investments and Other AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member] Accumulated Other Comprehensive Income (Loss) Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income (Loss) [Line Items] Before Tax AOCI Attributable To Parent, Before Tax [Roll Forward] AOCI Attributable To Parent, Before Tax [Roll Forward] Balance AOCI before Tax, Attributable to Parent Changes in value OCI, before Reclassifications, before Tax, Attributable to Parent Amounts reclassified to earnings Reclassification from AOCI, Current Period, before Tax, Attributable to Parent Balance Deferred Tax AOCI Attributable To Parent, Tax [Roll Forward] AOCI Attributable To Parent, Tax [Roll Forward] Balance AOCI Tax, Attributable to Parent Changes in value Other Comprehensive Income (Loss) before Reclassifications, Tax Amounts reclassified to earnings Reclassification from AOCI, Current Period, Tax Balance Net of Tax AOCI Attributable to Parent, Net of Tax [Roll Forward] Changes in value OCI, before Reclassifications, Net of Tax, Attributable to Parent Amounts reclassified to earnings Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent EMPLOYEE BENEFIT PLANS Compensation and Employee Benefit Plans [Text Block]