Exhibit 10.21
                 THIRD AMENDMENT TO ASSET ACQUISITION AGREEMENT

     This  THIRD  AMENDMENT  TO  ASSET   ACQUISITION   AGREEMENT  (this  "Second
Amendment"),  dated as of February 28, 2005, is by and among Southwest  Airlines
Co., a Texas  corporation  ("Southwest"),  and ATA  Holdings  Corp.,  an Indiana
corporation  ("Holdings") and its wholly-owned subsidiary ATA Airlines, Inc., an
Indiana  corporation  ("ATA")  (Holdings  and  ATA as  debtors  and  debtors  in
possession are  collectively  referred to as "Sellers" and each  individually is
referred to as "Seller").

                                 R E C I T A L S

     WHEREAS,  Southwest,  Holdings  and ATA  entered  into that  certain  Asset
Acquisition  Agreement (the  "Agreement") as of December 22, 2004,  pursuant and
subject to the terms and  conditions of which,  among other things,  the Sellers
agreed to sell,  assign and  transfer  to  Southwest,  and  Southwest  agreed to
purchase  and acquire  from  Sellers,  certain  assets,  rights,  interests  and
properties of Sellers as described therein;

     WHEREAS,  the Sellers and Southwest are parties to a the First Amendment to
Asset   Acquisition   Agreement  dated  as  of  January  31,  2005  (the  "First
Amendment"), and the Second Amendment to Asset Acquisition Agreement dated as of
February 15, 2005 (the "Second Amendment")  pursuant to which the parties agreed
to extend the  expiration  date for the  assignment of the Midway Hangar and the
Midway Hangar Property;

     WHEREAS,  the Sellers and Southwest desire to further extend the expiration
date for the assignment of the Midway Hangar and Midway Hangar Property to March
15, 2005.

                               A G R E E M E N T S

     NOW, THEREFORE, in consideration of the mutual agreements contained herein,
and subject to the terms and conditions  hereof, the parties hereto hereby agree
as follows:

          1.  Definitions.  All capitalized terms used but not elsewhere defined
     herein  shall have the  respective  meanings  ascribed to such terms in the
     Agreement.

          2.  Amendment to  Agreement.  The Agreement is amended by deleting the
     current version of Section  12.3(b)(iii)  in its entirety and  substituting
     the following version in lieu thereof:

               (iii) if the Closing  shall not have  occurred on or before March
          15, 2005.

     3.  Continued  Force and  Effect.  The  Agreement,  as amended by the First
Amendment,  the Second Amendment,  and this Third Amendment,  and each and every
provision,  covenant,  representation,  warranty,  condition and right contained
therein, as amended by this Third Amendment,  is hereby ratified and affirmed as
of the date hereof, and shall continue in full force and effect.

     4.  Counterparts.  This  Third  Amendment  may be  executed  in one or more
counterparts,  each of which shall constitute an original and all of which, when
taken together, shall constitute one agreement.

     4. Governing Law. This Third  Amendment and the legal  relations  among the
parties  hereto shall be governed by and construed in accordance  with the rules
and  substantive  Laws of the State of New York,  without regard to conflicts of
law provisions thereof.






     IN WITNESS WHEREOF, this Third Amendment has been executed and delivered by
each of the parties  hereto by a duly  authorized  officer of each such party on
the date first set forth above.

                                    SELLERS:
                                    ATA HOLDINGS CORP.

                                    By:      /s/ Gilbert F. Viets
                                    Name:    Gilbert F. Viets
                                    Title:   Executive Vice President
                                             Chief Financial Officer

                                    ATA AIRLINES, INC.
.
                                    By:      /s/ Gilbert F. Viets
                                    Name:    Gilbert F. Viets
                                    Title:   Executive Vice President
                                             Chief Financial Officer


                                    SOUTHWEST:

                                    SOUTHWEST AIRLINES CO.
                                    By:      /s/ Laura Wright
                                    Name:    Laura Wright
                                    Title:   Sr. Vice President and Chief
                                             Financial Officer