Exhibit 4.1


                         FIRST SUPPLEMENTAL INDENTURE (this "First
                    Supplemental Indenture") dated as of December 21, 1999,
                    among AMTRAN, INC., an Indiana corporation, as issuer (the
                    "Company"), American Trans Air, Inc., Ambassadair Travel
                    Club, Inc., ATA Leisure Corp. (formerly known as ATA
                    Vacations, Inc.), Amber Travel, Inc., American Trans Air
                    Training Corporation, American Trans Air Execujet, Inc.,
                    Amber Air Freight Corporation (each, an Indiana
                    corporation) (the "Original Guarantors") and Chicago
                    Express Airlines, Inc., (a Georgia Corporation), ("Chicago
                    Express" and together with the Original Guarantors, the
                    "Guarantors"), as guarantors and First Security Bank,
                    N.A., a national banking association, as trustee (the
                    "Trustee").

          WHEREAS each of the Company, the Original Guarantors and the Trustee
have heretofore executed and delivered to the Trustee an Indenture (the
"Indenture"), dated as of July 24, 1997, providing for the issuance of the
Company's 10 1/2% Senior Notes due 2004 (the "Notes", which term shall include
any additional notes (the "Additional Notes") issued under the Indenture as
supplemented hereby on or after the date hereof;

          WHEREAS Section 2.03 of the Indenture provides that subject to
Article Four the aggregate principal amount of Notes which may be
authenticated and delivered under the Indenture is unlimited;

          WHEREAS Section 2.15 of the Indenture permits the Company, subject
to certain conditions, to issue Additional Notes under the Indenture which,
together with the Notes issued heretofore, shall be treated as a single class
for all purposes under the Indenture;

          WHEREAS Section 9.01(1) of the Indenture provides that without
notice to or the consent of any Holders, the Company and the Guarantors, when
authorized by a resolution of their Board of Directors, and the Trustee may
amend or supplement the Indenture to cure any ambiguity, defect or
inconsistency and Section 9.01(7) of the Indenture provides that without
notice to or the consent of any Holders, the Company and the Guarantors, when
authorized by a resolution of their Board of Directors, and the Trustee may
amend or supplement the Indenture to make any change that does not


<PAGE>


                                                                             2


adversely affect the rights of any Holder in any material
respect;

          WHEREAS the purpose of this First Supplemental Indenture is (i) to
make conforming adjustments to the Indenture with respect to the issuance of
Additional Notes as contemplated by Section 2.15 of the Indenture and (ii) to
cause Chicago Express Airlines, Inc. to provide a Subsidiary Guarantee of the
Notes containing the same provisions as those contemplated by Section 4.07 of
the Indenture; and

          WHEREAS the Company has requested that the Trustee execute and
deliver this First Supplemental Indenture and all requirements necessary to
make this First Supplemental Indenture a valid instrument in accordance with
its terms, and the execution and delivery of this First Supplemental Indenture
have been duly authorized in all respects.


          NOW THEREFORE, the Company, the Guarantors and the Trustee hereby
agree that the following Sections of this First Supplemental Indenture
supplement and amend the Indenture with respect to the issuance of Additional
Notes proposed to be issued thereunder on or after the date of this First
Supplemental Indenture:

          SECTION 1. Definitions. (a) Capitalized terms used herein and not
defined herein have the meanings ascribed to such terms in the Indenture.

          (b) Solely for purposes of this First Supplemental Indenture and any
Additional Notes originally issued under the Indenture on or after the date of
this First Supplemental Indenture, the following terms shall have the
indicated meanings (such meanings shall apply equally to both the singular and
plural forms of the respective terms):

          "Closing Date", solely for the purposes of Section 2.03 with respect
to Additional Notes, means the date on which any Additional Notes are
originally issued under the Indenture on or after the date of this First
Supplemental Indenture.

          "Exchange Notes" means any securities of the Company containing
terms identical to the Notes (except that such Exchange Notes shall be
registered under the Securities Act) that are issued and exchanged for the
Notes pursuant to a Registration Rights Agreement and the Indenture.

          "Guarantors" means American Trans Air, Inc., Ambassadair Travel
Club, Inc., ATA Leisure Corp. (formerly



<PAGE>


                                                                             3


known as ATA Vacations, Inc.), Amber Travel, Inc., American Trans Air Training
Corporation, American Trans Air Execujet, Inc. and Amber Air Freight
Corporation (each, an Indiana corporation) and Chicago Express, until a
successor replaces any Guarantor pursuant to Article Five of the Indenture and
thereafter means the successor of such Guarantor, and any Restricted
Subsidiary that executes a Subsidiary Guarantee.

          "Registration Rights Agreement" means a registration rights
agreement, among the Company, the Guarantors and one or more investment banks
that act as initial purchasers in the distribution of Notes, including the
Registration Rights Agreement dated as of December 21, 1999 between the
Company, the Guarantors and Deutsche Bank Securities Inc.

          "Registration Statement" means a Registration Statement as defined
and described in a Registration Rights Agreement.

          "Shelf Registration Statement" has the meaning provided in a
Registration Rights Agreement.

          SECTION 2. Payment of Interest. Whenever Additional Notes are issued
that will constitute restricted securities under the Securities Act of 1933,
interest on such Additional Notes will accrue from the date of original issue
of such Additional Notes. Certificates representing such Additional Notes may
bear a legend to the foregoing effect.

          SECTION 3. Subsidiary Guarantee. (a) Pursuant to Section 4.07,
Chicago Express, a Restricted Subsidiary of the Company, hereby provides a
Subsidiary Guarantee of payment of the Notes as set forth below.

          (b) Subject to the provisions of this Section 3, Chicago Express, as
primary obligor and not merely as surety, hereby fully, unconditionally and
irrevocably guarantees on a senior basis to each Holder and to the Trustee on
behalf of the Holders (a "Subsidiary Guarantee"): (i) the due and punctual
payment of the principal of, premium, if any, on and interest on each Note,
when and as the same shall become due and payable, whether, by acceleration,
required repurchase (including by reason of Change of Control), call for
redemption or otherwise, the due and punctual payment of interest on the
overdue principal of and interest, if any, on the Notes, to the extent lawful
(in each case including interest accruing on or after filing of any petition
in bankruptcy or reorganization relating to the Company or any Guarantor,


<PAGE>


                                                                             4


whether or not a claim for post filing interest is allowed in such
proceeding), and the due and punctual performance of all other obligations of
the Company to the Holders or the Trustee, all in accordance with the terms of
such Note and the Indenture and (ii) in the case of any extension of time of
payment or renewal of any Note or any of such other obligations, that the same
will be promptly paid in full when due or performed in accordance with the
terms of the extension or renewal, at Stated Maturity, by acceleration,
required repurchase (including by reason of Change of Control), call for
redemption or otherwise. Chicago Express hereby waives diligence, presentment,
demand of payment, filing of claims with a court in the event of merger or
bankruptcy of the Company, any right to require a proceeding first against the
Company, the benefit of discussion, protest or notice with respect to any such
Note or the debt evidenced thereby and all demands whatsoever, and covenants
that this Subsidiary Guarantee will not be discharged as to any such Note
except by payment in full of the principal thereof and interest thereon and as
provided in Section 8.01 and Section 8.02 (subject to Section 8.06) of the
Indenture. The obligations of Chicago Express hereunder shall not be affected
by any failure or delay of the Trustee to exercise any right or remedy under
this First Supplemental Indenture, the Indenture, the Notes or this Subsidiary
Guarantee. The maturity of the obligations guaranteed hereby may be
accelerated as provided in Article Six of the Indenture for the purposes of
this Section 3. In the event of any declaration of acceleration of such
obligations as provided in Article Six of the Indenture, such obligations
(whether or not due and payable) shall forthwith become due and payable by the
Guarantors for the purpose of this Section 3. In addition, without limiting
the foregoing provisions, upon the effectiveness of an acceleration under
Article Six of the Indenture, the Trustee shall promptly make a demand for
payment on the Notes under the Subsidiary Guarantee provided for in this
Section 3.

          The Subsidiary Guarantee shall remain in full force and effect and
continue to be effective should any petition be filed by or against the
Company for liquidation or reorganization, should the Company become insolvent
or make an assignment for the benefit of creditors or should a receiver or
trustee be appointed for all or any significant portion of the Company's
assets, and if the Trustee or the Holder of any Note is required by any court
or otherwise to return to the Company or any Guarantor, or any custodian,
receiver, liquidator, trustee, sequestrator or other similar official acting
in relation to the Company or the Guarantors, any amount paid to the Trustee
or such Holder in respect of a Note, this Subsidiary Guarantee, to the extent



<PAGE>


                                                                             5


theretofore discharged, shall continue to be effective or be reinstated in
full force and effect, as the case may be, all as though such payment has not
been made. Chicago Express further agrees, to the fullest extent that it may
lawfully do so, that, as between the Guarantors, on the one hand, and the
Holders and the Trustee, on the other hand, the maturity of the obligations
guaranteed hereby may be accelerated as provided in Article Six of the
Indenture for the purposes of this Subsidiary Guarantee, notwithstanding any
stay, injunction or other prohibition extant under any applicable bankruptcy
law preventing such acceleration in respect of the obligations Guaranteed
hereby.

          Chicago Express hereby irrevocably waives any claim or other rights
which it may now or hereafter acquire against the Company that arise from the
existence, payment, performance or enforcement of its obligations under this
Subsidiary Guarantee and the Indenture, including, without limitation, any
right of subrogation, reimbursement, exoneration, contribution,
indemnification, any right to participate in any claim or remedy of the
Holders against the Company or any collateral which any such Holder or the
Trustee on behalf of such Holder hereafter acquires, whether or not such
claim, remedy or right arises in equity, or under contract, statute or common
law, including, without limitation, the right to take or receive from the
Company, directly or indirectly, in cash or other property or by set-off or in
any other manner, payment or security on account of such claim or other rights
until such time as the Notes and all of the Company's other obligations being
guaranteed hereby shall have been indefeasibly paid in full. If any amount
shall be paid to the Guarantors in violation of the preceding sentence and the
principal of, premium, if any, and accrued interest on the Notes shall not
have been paid in full, such amount shall be deemed to have been paid to the
Guarantors for the benefit of, and held in trust for the benefit of, the
Holders, and shall forthwith be paid to the Trustee for the benefit of the
Holders to be credited and applied upon the principal of, premium, if any, and
accrued interest on the Notes. Each of the Guarantors acknowledges that it
will receive direct and indirect benefits from the issuance of the Notes
pursuant to the Indenture and that the waivers set forth in this Section 3 are
knowingly made in contemplation of such benefits.

          The Subsidiary Guarantee set forth in this Section 3 shall not be
valid or become obligatory for any purpose with respect to a Note until the
certificate of authentication on such Note shall have been signed by or on
behalf of the Trustee.




<PAGE>


                                                                             6


          (c) Subject to Section 3(f), nothing contained in this Section 3 or
elsewhere in the Indenture or in the Notes is intended to or shall impair, as
among any Guarantor and the Holders, the obligation of such Guarantor, which
is absolute, unconditional and irrevocable, upon failure by the Company, to
pay to the Holders the principal of, premium, if any, and interest on the
Notes as and when the same shall become due and payable in accordance with
their terms, or is intended to or shall affect the relative rights of the
Holders and creditors of such Guarantor, nor shall anything herein or therein
prevent the Holder of any Note or the Trustee on their behalf from exercising
all remedies otherwise permitted by applicable law upon default under this
Indenture.

          Without limiting the foregoing, nothing contained in this Section 3
will restrict the right of the Trustee or the Holders to take any action to
declare the Subsidiary Guarantee to be due and payable prior to the Stated
Maturity of the Notes pursuant to Section 6.02 of the Indenture or to pursue
any rights or remedies hereunder.

          (d) Chicago Express shall give prompt written notice to the Trustee
of any fact known to it which would prohibit the making of any payment to or
by the Trustee in respect of the Subsidiary Guarantee pursuant to the
provisions of this Section 3.

          (e) The failure to make a payment on account of principal of,
premium, if any, or interest on the Notes by reason of any provision of this
Section 3 will not be construed as preventing the occurrence of an Event of
Default.

          (f) Notwithstanding any other provision of the Indenture or the
Notes, the Subsidiary Guarantee shall not be enforceable against Chicago
Express in an amount in excess of the net worth of Chicago Express at the time
that determination of such net worth is, under applicable law, relevant to the
enforceability of the Subsidiary Guarantee. Such net worth shall include any
claim of any Subsidy against the Company for reimbursement and any claim
against any grantor of a Subsidiary Guarantee or Note Guarantee for
contribution.

          (g) Notwithstanding any other provision of the Indenture or the
Notes, this Subsidiary Guarantee shall be automatically and unconditionally
released and discharged upon (i) any sale, exchange or transfer, to any Person
not an Affiliate of the Company, of all of the Company's and each Restricted
Subsidiary's Capital Stock in, or all or



<PAGE>


                                                                             7


substantially all the assets of, such Restricted Subsidiary (which sale,
exchange or transfer is not prohibited by the Indenture) or (ii) the release
or discharge of the Guarantee which resulted in the creation of this
Subsidiary Guarantee, except a discharge or release by or as a result of
payment under such Guarantee.

SECTION 4. Additional Interest; Legends. Unless and until a Note is exchanged
for an Exchange Note pursuant to a Registration Rights Agreement, each Note
shall bear the legend set forth below on the face thereof.

          IF (I) THE SHELF REGISTRATION STATEMENT OR EXCHANGE OFFER
REGISTRATION STATEMENT, AS APPLICABLE UNDER THE REGISTRATION RIGHTS AGREEMENT,
IS NOT FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON OR PRIOR TO 45
DAYS AFTER THE CLOSING DATE, (II) THE EXCHANGE OFFER REGISTRATION STATEMENT OR
THE SHELF REGISTRATION STATEMENT, AS THE CASE MAY BE, IS NOT DECLARED
EFFECTIVE WITHIN 150 DAYS AFTER THE CLOSING DATE, (III) THE REGISTERED
EXCHANGE OFFER IS NOT CONSUMMATED ON OR PRIOR TO THE 30TH DAY AFTER THE DATE
ON WHICH THE EXCHANGE OFFER REGISTRATION STATEMENT WAS DECLARED EFFECTIVE, OR
(IV) THE SHELF REGISTRATION STATEMENT IS FILED AND DECLARED EFFECTIVE BUT
SHALL THEREAFTER CEASE TO BE EFFECTIVE AT ANY TIME PRIOR TO THE SECOND
ANNIVERSARY OF ITS EFFECTIVE DATE (OTHER THAN AFTER SUCH TIME AS ALL NOTES
HAVE BEEN DISPOSED OF)IN ACCORDANCE WITH THE TERMS OF THE REGISTRATION RIGHTS
AGREEMENT, THEN ADDITIONAL INTEREST ("ADDITIONAL INTEREST") SHALL ACCRUE ON
THE PRINCIPAL AMOUNT OF THIS NOTE, (A) IN THE CASE OF (I) ABOVE, COMMENCING ON
THE DAY AFTER EITHER SUCH REQUIRED FILING DATE, AT A RATE OF .50% PER ANNUM
FOR THE FIRST 90 DAYS IMMEDIATELY FOLLOWING EACH SUCH FILING DATE, SUCH
ADDITIONAL INTEREST INCREASING BY AN ADDITIONAL 0.50% PER ANNUM AT THE
BEGINNING OF EACH SUBSEQUENT 90-DAY PERIOD; (B) IN THE CASE OF (II) ABOVE,
COMMENCING ON THE DAY AFTER EITHER SUCH REQUIRED EFFECTIVE DATE, AT A RATE OF
 .50% PER ANNUM FOR THE FIRST 90 DAYS IMMEDIATELY FOLLOWING EACH SUCH FILING
DATE, SUCH ADDITIONAL INTEREST INCREASING BY AN ADDITIONAL 0.50% PER ANNUM AT
THE BEGINNING OF EACH SUBSEQUENT 90-DAY PERIOD; (C) IN THE CASE OF (III)
ABOVE, COMMENCING ON THE 31ST DAY AFTER SUCH EFFECTIVE DATE, AT A RATE OF .50%
PER ANNUM FOR THE FIRST 90 DAYS IMMEDIATELY FOLLOWING EACH SUCH FILING DATE,
SUCH ADDITIONAL INTEREST INCREASING BY AN ADDITIONAL 0.50% PER ANNUM AT THE
BEGINNING OF EACH SUBSEQUENT 90-DAY PERIOD; OR (D) IN THE CASE OF (IV) ABOVE,
COMMENCING ON THE DAY AFTER SUCH SHELF REGISTRATION STATEMENT CEASES TO BE
EFFECTIVE, AT A RATE OF .50% PER ANNUM FOR THE FIRST 90 DAYS IMMEDIATELY
FOLLOWING EACH SUCH FILING DATE, SUCH ADDITIONAL INTEREST INCREASING BY AN
ADDITIONAL 0.50% PER ANNUM AT THE BEGINNING OF EACH SUBSEQUENT 90-DAY PERIOD;
PROVIDED, HOWEVER, THAT



<PAGE>


                                                                             8


THE ADDITIONAL INTEREST RATE ON THE NOTES MAY NOT EXCEED IN THE AGGREGATE
2.0%; PROVIDED FURTHER, HOWEVER, THAT ANY AND ALL AMOUNTS OF ADDITIONAL
INTEREST PAID IN ACCORDANCE WITH SECTION 1 OF THIS NOTE SHALL BE CREDITED
AGAINST THE ADDITIONAL INTEREST SET FORTH ABOVE.

          SECTION 5. This First Supplemental Indenture. This First
Supplemental Indenture shall be construed as supplemental to the Indenture and
shall form a part of it, and the Indenture is hereby incorporated by reference
herein and each is hereby ratified, approved and confirmed.

          SECTION 6. GOVERNING LAW. THIS FIRST SUPPLEMENTAL INDENTURE SHALL BE
GOVERNED AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK.

          SECTION 7. Counterparts. This First Supplemental Indenture may be
executed in two or more counterparts, each of which shall constitute an
original, but all of which when taken together shall constitute but one
instrument.

          SECTION 8. Headings. The headings of this First Supplemental
Indenture are for reference only and shall not limit or otherwise affect the
meaning hereof.

          SECTION 9. Trustee Not Responsible for Recitals. The recitals herein
contained are made by the Company and not by the Trustee, and the Trustee
assumes no responsibility for the correctness thereof. The Trustee shall not
be responsible in any manner whatsoever for or in respect of the validity or
sufficiency of this First Supplemental Indenture.

          SECTION 10. Separability. In case any one or more of the provisions
contained in this First Supplemental Indenture shall for any reason be held to
be invalid, illegal or unenforceable in any respect, such invalidity,
illegality or unenforceability shall not affect any other provisions of this
First Supplemental Indenture, but this First Supplemental Indenture shall be
construed as if such invalid or illegal or unenforceable provision had never
been contained herein.


          IN WITNESS WHEREOF, the parties hereto have caused this First
Supplemental Indenture to be duly executed by their respective authorized
officers as of the date first written above.



<PAGE>


                                                                             9



                                             AMTRAN, INC.,
                                                as Issuer,

                                                by: /s/ Kenneth K. Wolff
                                                    ---------------------------
                                                      Name:  Kenneth K. Wolff
                                                      Title: Executive Vice
                                                             President & CFO


                                             AMERICAN TRANS AIR, INC.,
                                                as Guarantor,

                                                by: /s/ Kenneth K. Wolff
                                                    ---------------------------
                                                      Name:  Kenneth K. Wolff
                                                      Title: Executive Vice
                                                             President & CFO


                                             AMBASSADAIR TRAVEL CLUB, INC.,
                                                as Guarantor,

                                                by: /s/ Kenneth K. Wolff
                                                    ---------------------------
                                                      Name:  Kenneth K. Wolff
                                                      Title: Executive Vice
                                                             President & CFO


                                             ATA LEISURE CORP. (formerly known
                                             as ATA VACATIONS, INC.),
                                                 as Guarantor,

                                                by: /s/ Kenneth K. Wolff
                                                    ---------------------------
                                                      Name:  Kenneth K. Wolff
                                                      Title: Executive Vice
                                                             President & CFO


                                             AMBER TRAVEL, INC.,
                                               as Guarantor

                                                by: /s/ Kenneth K. Wolff
                                                    ---------------------------
                                                      Name:  Kenneth K. Wolff
                                                      Title: Executive Vice
                                                             President & CFO



<PAGE>


                                                                            10


                                             AMERICAN TRANS AIR TRAINING
                                             CORPORATION,
                                                as Guarantor,

                                                by: /s/ Kenneth K. Wolff
                                                    ---------------------------
                                                      Name:  Kenneth K. Wolff
                                                      Title: Executive Vice
                                                             President & CFO


                                             AMERICAN TRANS AIR EXECUJET, INC.,
                                                as Guarantor,

                                                by: /s/ Kenneth K. Wolff
                                                    ---------------------------
                                                      Name:  Kenneth K. Wolff
                                                      Title: Executive Vice
                                                             President & CFO


                                             AMBER AIR FREIGHT CORPORATION,
                                                as Guarantor,

                                                by: /s/ Kenneth K. Wolff
                                                    --------------------------
                                                      Name:  Kenneth K. Wolff
                                                      Title: Executive Vice
                                                             President & CFO


                                             CHICAGO EXPRESS AIRLINES, INC.,
                                                as Guarantor,

                                                by: /s/ Stephen Cooper
                                                    ---------------------------
                                                      Name:  Stephen Cooper
                                                      Title: Acting President


<PAGE>


                                                                            11


                                             FIRST SECURITY BANK, N.A.,
                                                as Trustee,

                                               by /s/ Greg A. Hawley
                                                  -----------------------------
                                                 Name:  Greg A. Hawley
                                                 Title: Vice President