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

                                  -------------

                                  SCHEDULE 13D

                    UNDER THE SECURITIES EXCHANGE ACT OF 1934
                               (AMENDMENT NO. 3)*

                              TransAlta Corporation
 -------------------------------------------------------------------------------
                                (Name of Issuer)

                                  Common Stock
 -------------------------------------------------------------------------------
                         (Title of Class of Securities)

                                    89346D107
 -------------------------------------------------------------------------------
                                 (CUSIP Number)


                              Mr. Christopher Hohn
                            The Children's Investment
                            Fund Management (UK) LLP
                                7 Clifford Street
                                 London W1S 2WE
                                 United Kingdom
                                +44 20 7440 2330


                                 With a copy to:

                              Marc Weingarten, Esq.
                            Schulte Roth & Zabel LLP
                                919 Third Avenue
                            New York, New York 10022
                                 (212) 756-2000


 -------------------------------------------------------------------------------
                  (Name, Address and Telephone Number of Person
                Authorized to Receive Notices and Communications)

                         (Continued on following pages)

                                February 27, 2009
 -------------------------------------------------------------------------------
             (Date of Event which Requires Filing of This Statement)

If the filing person has previously filed a statement on Schedule 13G to report
the acquisition that is the subject of this Schedule 13D, and is filing this
schedule because of Rule 13d-1(e), 13d-1(f) or 13d-1(g), check the following
box. [ ]

NOTE: Schedules filed in paper format shall include a signed original and five
copies of the schedule, including all exhibits. See Rule 13d-7 for other parties
to whom copies are to be sent.

--------------------------
* 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
disclosures provided in a prior cover page. The information required on 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).

                               (Page 1 of 8 Pages)





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CUSIP NO.      89346D107            SCHEDULE 13D           PAGE 2 OF 8 Pages
--------------------------------------------------------------------------------

--------------------------------------------------------------------------------
    1       NAME OF REPORTING PERSON
            I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
            The Children's Investment Fund Management (UK) LLP
-----------------------------------------------------------------------------
    2       CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*       (a) [ ]
                                                                    (b) [ ]
-----------------------------------------------------------------------------
    3       SEC USE ONLY

-----------------------------------------------------------------------------
    4       SOURCE OF FUNDS*

            AF
-----------------------------------------------------------------------------
    5       CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO
            ITEMS 2(d) or 2(e)                                         [X]

-----------------------------------------------------------------------------
    6       CITIZENSHIP OR PLACE OF ORGANIZATION

            England
-----------------------------------------------------------------------------
    7       SOLE VOTING POWER

                                  -0-
-----------------------------------------------------------------------------
 NUMBER OF                 8      SHARED VOTING POWER
  SHARES
BENEFICIALLY                      9,804,900
  OWNED BY            -------------------------------------------------------
    EACH                   9      SOLE DISPOSITIVE POWER
 REPORTING
PERSON WITH                       -0-
                      -------------------------------------------------------
                           10     SHARED DISPOSITIVE POWER

                                  9,804,900
-----------------------------------------------------------------------------
    11      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

            4.96%
-----------------------------------------------------------------------------
    12      CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES
            CERTAIN SHARES*
                                                                        [ ]
-----------------------------------------------------------------------------
    13      PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

            4.96%
-----------------------------------------------------------------------------
    14      TYPE OF REPORTING PERSON*

            PN
-----------------------------------------------------------------------------





--------------------------------------------------------------------------------
CUSIP NO.      89346D107            SCHEDULE 13D           PAGE 3  OF  8 Pages
--------------------------------------------------------------------------------

--------------------------------------------------------------------------------
    1       NAME OF REPORTING PERSON
            I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
            The Children's Investment Fund Management (Cayman) Ltd.
-----------------------------------------------------------------------------
    2       CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*       (a) [ ]
                                                                    (b) [ ]
-----------------------------------------------------------------------------
    3       SEC USE ONLY

-----------------------------------------------------------------------------
    4       SOURCE OF FUNDS*

            AF
-----------------------------------------------------------------------------
    5       CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO
            ITEMS 2(d) or 2(e)                                         [X]

-----------------------------------------------------------------------------
    6       CITIZENSHIP OR PLACE OF ORGANIZATION

            Cayman Islands
-----------------------------------------------------------------------------
    7      SOLE VOTING POWER

                                  -0-
-----------------------------------------------------------------------------
NUMBER OF                 8      SHARED VOTING POWER
  SHARES
BENEFICIALLY                      9,804,900
  OWNED BY            -------------------------------------------------------
    EACH                   9      SOLE DISPOSITIVE POWER
 REPORTING
PERSON WITH                       -0-
                      -------------------------------------------------------
                           10     SHARED DISPOSITIVE POWER

                                  9,804,900
-----------------------------------------------------------------------------
    11      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

            4.96%
-----------------------------------------------------------------------------
    12      CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES
            CERTAIN SHARES*
                                                                        [ ]
-----------------------------------------------------------------------------
    13      PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

            4.96%
-----------------------------------------------------------------------------
    14      TYPE OF REPORTING PERSON*

            CO
-----------------------------------------------------------------------------





--------------------------------------------------------------------------------
CUSIP NO.      89346D107            SCHEDULE 13D           PAGE 4 OF 8 Pages
--------------------------------------------------------------------------------

--------------------------------------------------------------------------------
    1       NAME OF REPORTING PERSON
            I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
            The Children's Investment Master Fund
-----------------------------------------------------------------------------
    2       CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*       (a) [ ]
                                                                    (b) [ ]

-----------------------------------------------------------------------------
    3       SEC USE ONLY

-----------------------------------------------------------------------------
    4       SOURCE OF FUNDS*

            WC
-----------------------------------------------------------------------------
    5       CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO
            ITEMS 2(d) or 2(e)                                         [X]

-----------------------------------------------------------------------------
    6       CITIZENSHIP OR PLACE OF ORGANIZATION

            Cayman Islands
-----------------------------------------------------------------------------
    7       SOLE VOTING POWER

                                  -0-
-----------------------------------------------------------------------------
NUMBER OF                 8      SHARED VOTING POWER
  SHARES
BENEFICIALLY                      9,804,900
  OWNED BY            -------------------------------------------------------
    EACH                   9      SOLE DISPOSITIVE POWER
 REPORTING
PERSON WITH                       -0-
                      -------------------------------------------------------
                           10     SHARED DISPOSITIVE POWER

                                  9,804,900
-----------------------------------------------------------------------------
    11      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

            4.96%
-----------------------------------------------------------------------------
    12      CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES
            CERTAIN SHARES*
                                                                        [ ]
-----------------------------------------------------------------------------
    13      PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

            4.96%
-----------------------------------------------------------------------------
    14      TYPE OF REPORTING PERSON*

            CO
-----------------------------------------------------------------------------





--------------------------------------------------------------------------------
CUSIP NO.      89346D107            SCHEDULE 13D           PAGE 5 OF 8 Pages
--------------------------------------------------------------------------------

--------------------------------------------------------------------------------
    1       NAME OF REPORTING PERSON
            I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
            Christopher Hohn
-----------------------------------------------------------------------------
    2       CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*       (a) [ ]
                                                                    (b) [ ]

-----------------------------------------------------------------------------
    3       SEC USE ONLY

-----------------------------------------------------------------------------
    4       SOURCE OF FUNDS*

            AF
-----------------------------------------------------------------------------
    5       CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO
            ITEMS 2(d) or 2(e)                                         [X]

-----------------------------------------------------------------------------
    6       CITIZENSHIP OR PLACE OF ORGANIZATION

            United Kingdom
-----------------------------------------------------------------------------
    7       SOLE VOTING POWER

                                  -0-
-----------------------------------------------------------------------------
NUMBER OF                 8      SHARED VOTING POWER
  SHARES
BENEFICIALLY                      9,804,900
  OWNED BY            -------------------------------------------------------
    EACH                   9      SOLE DISPOSITIVE POWER
 REPORTING
PERSON WITH                       -0-
                      -------------------------------------------------------
                           10     SHARED DISPOSITIVE POWER

                                  9,804,900
-----------------------------------------------------------------------------
    11      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

            4.96%
-----------------------------------------------------------------------------
    12      CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES
            CERTAIN SHARES*
                                                                        [ ]
-----------------------------------------------------------------------------
    13      PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

            4.96%
-----------------------------------------------------------------------------
    14      TYPE OF REPORTING PERSON*

            IN
-----------------------------------------------------------------------------





--------------------------------------------------------------------------------
CUSIP NO.      89346D107            SCHEDULE 13D           PAGE  6 OF 8 Pages
--------------------------------------------------------------------------------


The Schedule 13D filed on August 15, 2008 (the "Schedule 13D"), as amended by
the Amendment No. 1 filed on September 10, 2008 and the Amendment No. 2 filed on
January 16, 2009 by The Children's Investment Fund Management (UK) LLP, an
English limited liability partnership, The Children's Investment Fund Management
(Cayman) Ltd., a Cayman Islands exempted company, The Children's Investment
Master Fund, a Cayman Islands exempted company, and Christopher Hohn (together,
the "Reporting Persons") relating to the shares ("Shares") of common stock of
TransAlta Corporation (the "Issuer"), is hereby amended as set forth below by
this Amendment No. 3 to the Schedule 13D.


ITEM 5.           INTEREST IN SECURITIES OF THE ISSUER

Paragraphs (a), (c) and (e) of Item 5 of the Schedule 13D are hereby amended and
restated as follows:

            (a) As of the close of business on February 27, 2009, the Reporting
Persons beneficially owned an aggregate of 9,804,900 Shares, constituting
approximately 4.96% of the Shares outstanding.

            The aggregate percentage of Shares beneficially owned by the
Reporting Persons is based upon 197,615,840 Shares outstanding, which is the
total number of Shares issued and outstanding as of September 30, 2008 as
reported in the Issuer's Amendment No. 1 to Form 10-F filed on November 18,
2008.

            (c) Information concerning transactions in the Shares effected by
the Reporting Persons since the last amendment is set forth in Appendix A hereto
and is incorporated herein by reference.

            (e) The reporting persons ceased to be the beneficial owners of more
than five percent of the Shares on February 27, 2009.





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CUSIP NO.      89346D107            SCHEDULE 13D           PAGE 7  OF 8  Pages
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                                   SIGNATURES

     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.

Dated:  March 6, 2009


                                    THE CHILDREN'S INVESTMENT FUND
                                    MANAGEMENT (UK) LLP


                                    /s/ Christopher Hohn
                                    ------------------------------
                                    Christopher Hohn
                                    Managing Partner



                                    THE CHILDREN'S INVESTMENT FUND
                                    MANAGEMENT (CAYMAN) LTD.


                                    /s/ David DeRosa
                                    ------------------------------
                                    David DeRosa
                                    Director



                                    THE CHILDREN'S INVESTMENT MASTER FUND


                                    /s/ David DeRosa
                                    ------------------------------
                                    David DeRosa
                                    Director


                                    /s/ Christopher Hohn
                                    ------------------------------
                                    Christopher Hohn





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CUSIP NO.      89346D107            SCHEDULE 13D           PAGE 8  OF 8  Pages
--------------------------------------------------------------------------------

                                   APPENDIX A

                   TRANSACTIONS IN THE SHARES EFFECTED BY THE
             REPORTING PERSONS SINCE THE FILING OF THE SCHEDULE 13D
           (UNLESS OTHERWISE STATED, ALL TRANSACTIONS WERE EFFECTED IN
                                THE OPEN MARKET)


        The Children's Investment Master Fund


          Date of Trade       Shares Purchased (Sold)      Price per Share(1)
            15-Jan-09                 (77,100)                   18.188
            15-Jan-09                 (34,000)                   18.201
            16-Jan-09                 (29,300)                   18.379
            22-Jan-09                  (6,300)                   17.507
            29-Jan-09                 (20,200)                   18.766
            30-Jan-09                 (40,345)                   18.392
            02-Feb-09                 (87,300)                   18.027
            03-Feb-09                (104,200)                   18.066
            04-Feb-09                (138,700)                   18.286
            04-Feb-09                (200,000)                   18.259
            05-Feb-09                 (84,000)                   18.128
            05-Feb-09                (100,000)                   18.218
            06-Feb-09                 (85,200)                   18.401
            09-Feb-09                 (50,000)                   18.621
            09-Feb-09                 (64,500)                   18.511
            10-Feb-09                 (66,700)                   17.595
            11-Feb-09                 (67,000)                   17.465
            12-Feb-09                (113,400)                   17.141
            13-Feb-09                 (95,900)                   17.352
            17-Feb-09                 (76,764)                   16.123
            27-Feb-09                (146,100)                   16.337
            02-Mar-09                 (93,100)                   15.535
            03-Mar-09                (124,900)                   15.134
            04-Mar-09                (229,900)                   15.012
            05-Mar-09                (136,100)                   14.162


---------------------
(1) US dollar amounts calculated using exchange rates in effect on the date of
trade.