Washington, D.C. 20549

                                 SCHEDULE 13G/A
                                 (Rule 13d-102)

           TO RULES 13d-1(b), (c) AND (d) AND AMENDMENTS THERETO FILED
                            PURSUANT TO RULE 13d-2(b)
                               (Amendment No. 1)*

                                 UAL Corporation
                                (Name of Issuer)

                   Common Stock, with $.01 par value per share
                         (Title of Class of Securities)

                                 (CUSIP Number)

                                February 28, 2007
             (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 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).

- -------------------------------------------------------------------------------- 1. NAMES OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) Impala Asset Management LLC 41-2118667 - -------------------------------------------------------------------------------- 2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (See Instructions) (a)[ ] (b)[X] - -------------------------------------------------------------------------------- 3. SEC USE ONLY - -------------------------------------------------------------------------------- 4. CITIZENSHIP OR PLACE OF ORGANIZATION State of Delaware - -------------------------------------------------------------------------------- 5. SOLE VOTING POWER 0 NUMBER OF ------------------------------------------------------------------ SHARES 6. SHARED VOTING POWER BENEFICIALLY 11,696,941 OWNED BY EACH ------------------------------------------------------------------ REPORTING 7. SOLE DISPOSITIVE POWER PERSON 0 WITH ------------------------------------------------------------------ 8. SHARED DISPOSITIVE POWER 11,696,941 - -------------------------------------------------------------------------------- 9. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 11,696,941 - -------------------------------------------------------------------------------- 10. CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (See Instructions) [ ] - -------------------------------------------------------------------------------- 11. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 10.56% - -------------------------------------------------------------------------------- 12. TYPE OF REPORTING PERSON (See Instructions) IA - --------------------------------------------------------------------------------

Item 1(a). Name of Issuer. UAL Corporation Item 1(b). Address of Issuer's Principal Executive Offices. 1200 E. Algonquin Road Elk Grove Township, IL 60007 Item 2(a).-(c). Names of Person Filing. Impala Asset Management LLC 134 Main Street New Caanan, CT 06840 Citizenship. Delaware Item 2(d). Title of Class of Securities. Common Shares with $.01 par value per share Item 2(e). CUSIP Number. 902549807 Item 3. If This Statement is Filed Pursuant to Rule 13d-1(b), or 13d-2(b) or (c), Check Whether the Person Filing is a: (a) [ ] Broker or dealer registered under Section 15 of the Exchange Act. (b) [ ] Bank as defined in Section 3(a)(6) of the Exchange Act. (c) [ ] Insurance company as defined in Section 3(a)(19) of the Exchange Act. (d) [ ] Investment company registered under Section 8 of the Investment Company Act. (e) [X] An investment adviser in accordance with Rule 13d-1(b)(1)(ii)(E); (f) [ ] An employee benefit plan or endowment fund in accordance with Rule 13d-1(b)(1)(ii)(F); (g) [ ] A parent holding company or control person in accordance with Rule 13d-1(b)(1)(ii)(G); (h) [ ] A savings association as defined in Section 3(b) of the Federal Deposit Insurance Act; (i) [ ] A church plan that is excluded from the definition of an investment company under Section 3(c)(14) of the Investment Company Act; (j) [ ] Group, in accordance with Rule 13d-1(b)(1)(ii)(J).

Item 4. Ownership. The information in items 1 and 5 through 11 on the cover pages (p. 2) on Schedule 13G is hereby incorporated by reference. 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. Not applicable. Item 7. Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person. Not applicable. Item 8. Identification and Classification of Members of the Group. Not applicable Item 9. Notice of Dissolution of Group. Not applicable.

Item 10. Certification. By signing below the undersigned certifies that, to the best of its knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect. SIGNATURE After reasonable inquiry and to the best of its knowledge and belief, the undersigned certifies that the information set forth in this statement is true, complete and correct. Date: March 9, 2007 Impala Asset Management LLC By: /s/ Thomas Sullivan ----------------------------------- Name: Thomas Sullivan Title: Chief Financial Officer