Page 1 of 13 Pages

                                   UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                            WASHINGTON, D.C.  20549

                                  SCHEDULE 13G

                     Under the Securities Exchange Act of 1934

                             (AMENDMENT NO.11)*

                               UAL CORP
            ------------------------------------------------------
                                (NAME OF ISSUER)

                                  COM PAR $0.01
            -----------------------------------------------------
                         (TITLE OF CLASS OF SECURITIES)

                                 902549500
            -----------------------------------------------------
                                (CUSIP NUMBER)

                                December 31, 1999
            -----------------------------------------------------
            (Date of Event Which Requires Filing of this Statement)

     Check the appropriate box to designate the rule pursuant to which
     this Schedule is filed:

    X  Rule 13d-1(b)
       Rule 13d-1(c)
       Rule 13d-1(d)

    * The remainder of this cover page shall be filled out for a reporting
    person`s initial filing on this form with respect to the subject class
    of securities, and for any subsequent amendment containing information
    which would alter the disclosures provided in a prior cover page.

    The information required in the remainder of this cover page shall not
    be deemed to be 'filed' for the purpose of Section 18 of the Securities
    Exchange Act of 1934 ('Act') or otherwise subject to the liabilities
    of that section of the Act but shall be subject to all other provisions
    of the Act (however, see the Notes).

                       (CONTINUED ON FOLLOWING PAGE(S))

CUSIP NO. 902549500 13G Page 2 of 13 Pages 1. NAME OF REPORTING PERSON S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON AXA Assurances I.A.R.D. Mutuelle 2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP * (A) [ ] (B) [X] 3. SEC USE ONLY 4. CITIZENSHIP OR PLACE OF ORGANIZATION France NUMBER OF SHARES 5. SOLE VOTING POWER 916,740 BENEFICIALLY OWNED AS OF 6. SHARED VOTING POWER 2,257,700 December 31, 1999 BY EACH 7. SOLE DISPOSITIVE POWER 4,328,450 REPORTING PERSON WITH: 8. SHARED DISPOSITIVE POWER 11,050 9. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 4,339,500 (Not to be construed as an admission of beneficial ownership) 10. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES * | | 11. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 8.1% 12. TYPE OF REPORTING PERSON * IC * SEE INSTRUCTIONS BEFORE FILLING OUT!

CUSIP NO. 902549500 13G Page 3 of 13 Pages 1. NAME OF REPORTING PERSON S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON AXA Assurances Vie Mutuelle 2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP * (A) [ ] (B) [X] 3. SEC USE ONLY 4. CITIZENSHIP OR PLACE OF ORGANIZATION France NUMBER OF SHARES 5. SOLE VOTING POWER 916,740 BENEFICIALLY OWNED AS OF 6. SHARED VOTING POWER 2,257,700 December 31, 1999 BY EACH 7. SOLE DISPOSITIVE POWER 4,328,450 REPORTING PERSON WITH: 8. SHARED DISPOSITIVE POWER 11,050 9. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 4,339,500 (Not to be construed as an admission of beneficial ownership) 10. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES * | | 11. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 8.1% 12. TYPE OF REPORTING PERSON * IC * SEE INSTRUCTIONS BEFORE FILLING OUT!

CUSIP NO. 902549500 13G Page 4 of 13 Pages 1. NAME OF REPORTING PERSON S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON AXA Conseil Vie Assurance Mutuelle 2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP * (A) [ ] (B) [X] 3. SEC USE ONLY 4. CITIZENSHIP OR PLACE OF ORGANIZATION France NUMBER OF SHARES 5. SOLE VOTING POWER 916,740 BENEFICIALLY OWNED AS OF 6. SHARED VOTING POWER 2,257,700 December 31, 1999 BY EACH 7. SOLE DISPOSITIVE POWER 4,328,450 REPORTING PERSON WITH: 8. SHARED DISPOSITIVE POWER 11,050 9. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 4,339,500 (Not to be construed as an admission of beneficial ownership) 10. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES * | | 11. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 8.1% 12. TYPE OF REPORTING PERSON * IC * SEE INSTRUCTIONS BEFORE FILLING OUT!

CUSIP NO. 902549500 13G Page 5 of 13 Pages 1. NAME OF REPORTING PERSON S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON AXA Courtage Assurance Mutuelle 2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP * (A) [ ] (B) [X] 3. SEC USE ONLY 4. CITIZENSHIP OR PLACE OF ORGANIZATION France NUMBER OF SHARES 5. SOLE VOTING POWER 916,740 BENEFICIALLY OWNED AS OF 6. SHARED VOTING POWER 2,257,700 December 31, 1999 BY EACH 7. SOLE DISPOSITIVE POWER 4,328,450 REPORTING PERSON WITH: 8. SHARED DISPOSITIVE POWER 11,050 9. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 4,339,500 (Not to be construed as an admission of beneficial ownership) 10. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES * | | 11. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 8.1% 12. TYPE OF REPORTING PERSON * IC * SEE INSTRUCTIONS BEFORE FILLING OUT!

CUSIP NO. 902549500 13G Page 6 of 13 Pages 1. NAME OF REPORTING PERSON S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON AXA 2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP * (A) [ ] (B) [X] 3. SEC USE ONLY 4. CITIZENSHIP OR PLACE OF ORGANIZATION France NUMBER OF SHARES 5. SOLE VOTING POWER 916,740 BENEFICIALLY OWNED AS OF 6. SHARED VOTING POWER 2,257,700 December 31, 1999 BY EACH 7. SOLE DISPOSITIVE POWER 4,328,450 REPORTING PERSON WITH: 8. SHARED DISPOSITIVE POWER 11,050 9. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 4,339,500 (Not to be construed as an admission of beneficial ownership) 10. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES * | | 11. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 8.1% 12. TYPE OF REPORTING PERSON * IC * SEE INSTRUCTIONS BEFORE FILLING OUT!

CUSIP NO. 902549500 13G Page 7 of 13 Pages 1. NAME OF REPORTING PERSON S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON AXA Financial, Inc. 13-3623351 (formerly known as The Equitable Companies Incorporated) 2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP * (A) [ ] (B) [X] 3. SEC USE ONLY 4. CITIZENSHIP OR PLACE OF ORGANIZATION State of Delaware NUMBER OF SHARES 5. SOLE VOTING POWER 911,840 BENEFICIALLY OWNED AS OF 6. SHARED VOTING POWER 2,257,700 December 31, 1999 BY EACH 7. SOLE DISPOSITIVE POWER 4,328,450 REPORTING PERSON WITH: 8. SHARED DISPOSITIVE POWER 550 9. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 4,329,000 (Not to be construed as an admission of beneficial ownership) 10. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES * | | 11. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 8.1% 12. TYPE OF REPORTING PERSON * HC * SEE INSTRUCTIONS BEFORE FILLING OUT!

Item 1(a) Name of Issuer: Page 8 of 13 Pages UAL CORP Item 1(b) Address of Issuer's Principal Executive Offices: ----------------------------------------------- 1200 E. Algonquin Road Elk Grove Vill., IL 60007 Item 2(a) and (b) Name of Person Filing and Address of Principal Business Office: AXA Conseil Vie Assurance Mutuelle, 100-101 Terrasse Boieldieu 92042 Paris La Defense France AXA Assurances I.A.R.D Mutuelle, and AXA Assurances Vie Mutuelle, 21, rue de Chateaudun 75009 Paris France AXA Courtage Assurance Mutuelle, 26, rue Louis le Grand 75002 Paris France as a group (collectively, the 'Mutuelles AXA'). AXA 9 Place Vendome 75001 Paris France AXA Financial, Inc. (formerly known as The Equitable Companies Incorporated) 1290 Avenue of the Americas New York, New York 10104 (Please contact Patrick Meehan at (212) 314-5644 with any questions.)

Page 9 of 13 Pages Item 2(c) Citizenship: Mutuelles AXA and AXA - France AXA Financial, Inc. - Delaware Item 2(d) Title of Class of Securities: COM PAR $0.01 Item 2(e) CUSIP Number: 902549500 Item 3. Type of Reporting Person: AXA Financial, Inc. as a parent holding company, in accordance with 240.13d-1(b)(ii)(G) The Mutuelles AXA, as a group, acting as a parent holding company. AXA as a parent holding company.

Page 10 of 13 Pages Item 4. Ownership as of December 31, 1999: (a) Amount Beneficially Owned: 4,339,500 shares of common stock beneficially owned including: No. of Shares --------------- The Mutuelles AXA, as a group 0 AXA 0 AXA Entity or Entities: AXA Rosenberg (U.S.) 10,500 Common Stock acquired solely for investment purposes. AXA Financial, Inc. 0 Subsidiaries: Alliance Capital Management L.P. acquired solely for investment purposes on behalf of client discretionary investment advisory accounts: Common Stock 4,315,450 4,315,450 ---------- Donaldson, Lufkin & Jenrette Securities Corporation held for investment purposes: Common Stock 550 550 ---------- The Equitable Life Assurance Society of the United States acquired solely for investment purposes. Common Stock 13,000 13,000 ---------- ----------- Total 4,339,500 =========== Each of the Mutuelles AXA, as a group, and AXA expressly declares that the filing of this Schedule 13G shall not be construed as an admission that it is, for purposes of Section 13(d) of the Exchange Act, the beneficial owner any securities covered by this Schedule 13G. Each of the above subsidiaries of AXA Financial, Inc. operates under independent management and makes independent decisions. (b) Percent of Class: 8.1% ===========

ITEM 4. Ownership as of 12/31/1999(CONT.) Page 11 of 13 Pages (c) Deemed Voting Power and Disposition Power: (i) (ii) (iii) (iv) Deemed Deemed Deemed Deemed to have to have to have to have Sole Power Shared Power Sole Power Shared Power to Vote to Vote to Dispose to Dispose or to or to or to or to Direct Direct Direct the Direct the the Vote the Vote Disposition Disposition ----------- ----------- ------------ ------------ The Mutuelles AXA, as a group 0 0 0 0 AXA 0 0 0 0 AXA Entity or Entities: AXA Rosenberg (U.S.) 4,900 0 0 10,500 AXA Financial, Inc 0 0 0 0 Subsidiaries: Alliance Capital Management L.P. 898,840 2,257,700 4,315,450 0 Donaldson, Lufkin & Jenrette Securities Corporation 0 0 0 550 The Equitable Life Assurance Society of the United States 13,000 0 13,000 0 ------------ ------------ ------------ ------------ TOTAL 916,740 2,257,700 4,328,450 11,050 ============ ============ ============ ============ Each of the above subsidiaries of AXA Financial, Inc. operates under independent management and makes independent voting and investment decisions.

Page 12 of 13 Pages Item 5. Ownership of Five Percent or Less of a Class: If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than five percent of the class of securities, check the following. ( ) Item 6. Ownership of More than Five Percent on behalf of Another Person. N/A Item 7. Identification and Classification of the Subsidiary which Acquired the Security Being Reporting on by the Parent Holding Company: This Schedule 13G is being filed by AXA Financial, Inc.; AXA, which beneficially owns a majority interest in AXA Financial, Inc.; and the Mutuelles AXA, which as a group control AXA: (X ) in the Mutuelles AXAs' capacity, as a group, acting as a parent holding company with respect to the holdings of the following AXA entity or entities; (X ) in AXA's capacity as a parent holding company with respect to the holdings of the following AXA entity or entities: AXA Rosenberg (U.S.) (X) in AXA Financial, Inc.'s capacity as a parent holding company with respect to the holdings of its following subsidiaries: (X) Alliance Capital Management L.P. (13-3434400), an investment adviser registered under Section 203 of the Investment Advisers Act of 1940. (X) Donaldson, Lufkin & Jenrette Securities Corporation (13-2741729), a broker-dealer registered under Section 15 of the Securities and Exchange Act of 1934 and an investment adviser registered under Section 203 of the Investment Advisers Act of 1940. (X) The Equitable Life Assurance Society of the United States (13-5570651), an insurance company, a broker-dealer registered under Section 15 of the Securities and Exchange Act of 1934 and an investment adviser registered under Section 203 of the Investment Advisers Act of 1940.

Page 13 of 13 Pages Item 8. Identification and Classification of Members of the Group. N/A Item 9. Notice of Dissolution of Group: N/A Item 10. Certification: By signing below I certify that to the best of my knowledge and belief, the securities referred to above were acquired in the ordinary course of business and were not acquired for the purpose of and do not have the effect of changing or influencing the control of the issuer of such securities and were not acquired in connection with or as a participant in any transaction having such purposes or effect. Signature After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct. Date: February 10, 2000 AXA FINANCIAL, INC.* /s/ Alvin H. Fenichel Senior Vice President and Controller *Pursuant to the Joint Filing Agreement with respect to Schedule 13G attached hereto as Exhibit I, among AXA Financial, Inc., AXA Conseil Vie Assurance Mutuelle, AXA Assurances I.A.R.D Mutuelle, AXA Assurances Vie Mutuelle, AXA Courtage Assurance Mutuelle, and AXA, this statement Schedule 13G is filed on behalf of each of them.

                                                                 EXHIBIT I



                                   JOINT FILING AGREEMENT




        Each of the undersigned hereby agrees that the Schedule 13G filed
   herewith is filed jointly, pursuant to Rule 13d-1(f)(1) of the Securities
   Exchange Act of 1934, as amended on behalf of each of them.


               Dated: February 10, 2000



               AXA Financial, Inc.



               BY:  /s/ Alvin H. Fenichel
                  -------------------------
                  Alvin H. Fenichel
                  Senior Vice President
                  and Controller



        AXA Assurances I.A.R.D. Mutuelle; AXA Assurances Vie Mutuelle; AXA
   Conseil Vie Assurance Mutuelle; AXA Courtage Assurance Mutuelle, as a
   group, and AXA

               Signed on behalf of each of the above entities



               BY:      /s/ Alvin H. Fenichel
                  Alvin H. Fenichel
                  Attorney-in-Fact
                  (Executed pursuant to Powers of Attorney)