<PAGE>   1


Confidential Treatment requested by Atlantic Southeast Airlines, Inc., File No.
0-11097


                                 EXHIBIT 10 (f)


                 Confidential treatment has been applied for with
                 respect to certain provisions of this Exhibit, which
                 provisions have been omitted from this Exhibit,
                 marked with an asterisk (*) and filed separately with
                 the SEC


<PAGE>   2

                             FOURTH AMENDMENT TO
                               CREDIT AGREEMENT
                           DATED DECEMBER 24, 1986

         This Fourth Amendment To Credit Agreement (this "Fourth Amendment") is
made and entered into this 17th day of September, 1996, by and among the
ATLANTIC SOUTHEAST AIRLINES, INC., a Georgia corporation (the "Company"), ASA
INVESTMENTS, INC., a Delaware Corporation ("Investments"), MANUFACTURERS
LEASING INTERNATIONAL CORP. ( "MHLI"), BANK OF AMERICA ILLINOIS [formerly known
as Continental Bank N.A. and Continental Illinois National Bank and Trust
Company of Chicago],  NATIONSBANK, N.A. (SOUTH) [formerly known as NationsBank
of Georgia, N.A. and Citizens and Southern National Bank], NATIONAL BANK OF
CANADA, THE ROYAL BANK OF CANADA, CANADIAN IMPERIAL BANK OF COMMERCE ("CIBC"),
KAWASAKI LEASING, (USA) INC. as successor in interest to Kawasaki Leasing
International, Inc. [formerly known as Kawasaki Lease Financing Inc.],
SOUTHTRUST BANK OF GEORGIA, N.A. [formerly known as First American Bank of
Georgia, N.A.] (all of such financial institutions are hereinafter collectively
referred to as the "Lenders").

                              W I T N E S S E T H:

         WHEREAS, the Company is indebted to the Lenders under the terms of
that certain Credit Agreement dated December 24, 1986, originally among the
Company, Investments, MHLI, and the financial institutions parties thereto as
respectively amended on each of February 20, 1987, May 23, 1989, and August 17,
1989 (said Credit Agreement as now or hereafter amended is hereinafter
collectively referred to as the "Credit Agreement"); and

         WHEREAS, CIBC has purchased the participation interest of each of
American Security Bank, N.A. ("American"), B.S.F.E. - Banque de la Societe
Financiere Europeenne ("BSFE"), and Barclays Bank, PLC ("Barclays") under the
Credit Agreement; and

         WHEREAS, SouthTrust Bank of Georgia, N.A. has succeeded to the
participation interest of First American Bank of Georgia, N.A. under the Credit
Agreement; and

         WHEREAS, effective November 30, 1995, Kawasaki Leasing, (USA) Inc. has
succeeded to the participation interest of Kawasaki Leasing International, Inc.
("KLII") under the Credit Agreement; and

         WHEREAS, the Company and Investments desire to obtain the approval and
consent of the necessary Lenders to implement a corporate reorganization and an
amendment to the Credit Agreement which will result in (i) each of the Company
and Investments becoming a wholly owned subsidiary of a holding company the
stock of which holding company is owned by the Company's current shareholders
and will be publicly traded, (ii) Investments being removed as a party to the
Credit Agreement and being relieved of its responsibility under any guarantee
thereof,

<PAGE>   3


and (iii) the Company being relieved of certain restrictions imposed under the
Credit Agreement; and

         WHEREAS, pursuant to the provisions of Section 11.04 of the Credit
Agreement, the parties desire to amend the Credit Agreement as hereinafter
provided.

         NOW, THEREFORE, for and in consideration of each party's agreement to
be bound hereby and other good, valuable and adequate consideration, the
parties hereto do hereby agree as follows:

         1.      All capitalized terms not otherwise specifically defined
herein shall have the meanings ascribed to them under the provisions of the
Credit Agreement.

         2.      Investments shall be removed as a party to the Credit
Agreement with all references to "ASA Investments, Inc." and "Investments"
under the Credit Agreement being hereby deleted in their entirety.
Additionally, from and after the date hereof, Investments shall not be
considered a "Subsidiary" (as defined and provided under the Credit Agreement)
of the Company notwithstanding any provision of the Credit Agreement to the
contrary.  In connection therewith, all parties agree that that certain
Guaranty dated as of December 24, 1986, delivered by Investments to MHLI in its
capacity as agent for the benefit of all Lenders (the "Guaranty") is hereby
terminated and shall be of no further force or effect it being the express
agreement of all parties that Investments shall have no obligations or
responsibilities to any one or more of the Lenders and that no Lender shall
have any claim or cause of action against Investments under or in connection
with the Credit Agreement, the credit extended to the Company thereunder, the
Basic Documents, or the Guaranty.  In addition, the definition of "Guaranty"
and all references to the "Guaranty" contained in the Credit Agreement or the
Basic Documents are hereby deleted.

         3.      All references to the "Company" or the "Subsidiaries" of the
Company under the Credit Agreement and all determinations required to be made
with respect thereto shall refer to and include solely and exclusively the
Company and its Subsidiaries (as defined in the Credit Agreement as modified by
this Fourth Amendment); provided, that in no event shall the Company's
Subsidiaries include (i) Investments, (ii) any parent or holding company owning
all or substantially all of the capital stock of  the Company or (iii) any
Person required to be included in any consolidated financial statement, tax
return or governmental filing covering the Company or  under any other
statement prepared or determination made in conformity with GAAP which Person
does not meet the definitional requirements of a "Subsidiary" of the Company
under the Credit Agreement.

         4.      The definitions of  "Indebtedness", "Tangible Net Worth",
"Total Assets" and "Total Liabilities" currently contained under Section 1.01
of the Credit Agreement are hereby amended in their entirety to read as
follows:




                                      2
                                        
<PAGE>   4

                 "Indebtedness" means [*]

                 "Tangible Net Worth" means as to any Person the Book Net Worth
of such Person minus (i) the amount, if any, of the Total Assets of such Person
and such Person's Subsidiaries which would be treated as intangibles under
GAAP, (ii) any write-up in the book value of any fixed asset resulting from a
revaluation thereof and (iii) the amount, if any, at which shares of capital
stock of such Person appear on the asset side of such Person's balance sheet.

                 "Total Assets" means as to any Person which is a corporation,
all items considered as assets for purposes of GAAP.

                 "Total Liabilities" means as to any Person which is a
corporation, all items considered as liabilities for purposes of GAAP.

         5.      The following definitions shall be added to Section 1.01 of
the Credit Agreement in the appropriate alphabetical order:

                 "Book Net Worth" means as to any Person the book value of the
Total Assets of such Person and such Person's Subsidiaries (exclusive of any
indebtedness owed to such Person or such Person's Subsidiaries by any affiliate
of such Person) which Total Assets are located within the United States of
America minus the book value of the Total Liabilities of such Person and its
Subsidiaries.  For purposes of clarity, marketable securities and commercial
paper issued by a foreign entity but held in the United States of America shall
be considered to be assets located within the United States of America.

                 "Capitalized Lease" means a capitalized lease of any tangible
real or personal property, as determined pursuant to GAAP.

                 "Current Maturities of Long Term Debt" means the amounts due,
within any twelve (12) month period following any fiscal quarter end of the
Company, under long-term debt instruments of the Company, as determined
pursuant to GAAP.

                  [*]

                  [*]

                 "GAAP" means generally accepted accounting principles as in
effect in the United States of America and applied on a basis consistent with
that used in the preparation of the Company's audited balance sheet for the
period ending December 31, 1995, and the related results of operation except
for (i) changes therein with which the Company's independent public accountants
concur that are disclosed in the notes to the relevant financial statements and
(ii) any requirements for consolidation inconsistent with the provisions of
Section 3 of the Fourth Amendment to this Agreement.




                                      3
                                        
<PAGE>   5


                 [*]

                 [*]

                 [*]

                 "Recent SEC Filings" means collectively (i) the Company's
annual report on Form 10-K for the year ended December 31, 1995 and (ii) the
Company's quarterly reports on Forms 10-Q for the calendar quarters ending
March 31, 1996 and June 30, 1996.

                 "Subject Reorganization" means the pending proposed
transaction under which (i) the Company shall form a wholly owned Subsidiary
("Holding Company"), (ii) Holding Company shall form a wholly owned subsidiary
("Second Level Subsidiary"), (iii) Second Level Subsidiary shall merge with and
into the Company with the Company surviving and (a) the Company shareholders
receiving stock in the Holding Company in exchange for the outstanding stock in
the Company, (b) the Holding Company receiving all capital stock in the
Company, and (c) all capital stock in the Holding Company owned by the Company
being canceled, and (iv) the Company's subsequent dividend distribution to the
Holding Company of all capital stock in Investments; all of which transactions
shall result in the Company and Investments becoming wholly owned subsidiaries
of Holding Company.

         6.      The representations and warranties contained under Sections
5.01 through 5.19 of the Credit Agreement (with all references to "this
Agreement" or "herein" (contained under such Sections to include in particular
the Credit Agreement as amended by this Fourth Amendment) as they pertain to
the Company are hereby re-affirmed or made (as applicable) by the Company as of
the date hereof, provided that, Section 5.10 is being reaffirmed as if "1985"
were "1995" therein.  The representations and warranties contained under
Sections 5.04, 5.05, 5.06, 5.11, 5.12, 5.13, 5.15, and 5.18 are hereby amended
and restated in their entirety as follows:

                 "SECTION 5.04 -- Litigation. [*]

                 SECTION 5.05 -- Financial Statements.  (a) The audited balance
sheet as of December 31, 1995, and the unaudited balance sheet as of June 30,
1996, and the related statement of operations for the year (audited) and
quarters (unaudited) then ended and the statements of reconciliations of the
shareholders' equity of the Company (copies of which have been furnished to
Lenders) have been prepared in accordance with generally accepted accounting
principles on a consistent basis with prior years and fairly present the
correct and complete financial condition of the Company as of such dates and
the results of the operations of the Company for such periods, and there has
been no material adverse change of the financial condition or operations of the
Company since June 30, 1996.

                 SECTION 5.06 -- Title to Properties.  The Company has good
title to its properties and assets except for defects which do not materially
affect the operation or financial



                                      4

                                        
<PAGE>   6

condition of the Company.  There are no liens, mortgages, security interests,
or other encumbrances of any of the items constituting Collateral under the
Security Agreements except those granted and held in favor of the Lenders.

                 SECTION 5.11 -- Status as United States Citizen".  The Company
is a "citizen of the United States" as that term is used in 49 U.S.C. Section
40102(a)(15), and is an air carrier holding a valid air carrier operating
certificate issued pursuant to 49 U.S.C. Chapter 447 for aircraft capable of
carrying 10 or more individuals.

                 SECTION 5.12 -- Indebtedness.  The Company has no indebtedness
for money borrowed except as disclosed under the Recent SEC Filings.

                 SECTION 5.13 -- Contingent Liabilities. The Company has no
contingent liabilities except as disclosed under the Recent SEC Filings.

                 SECTION 5.15 -- Forms 10-K and 10-Q.  The Recent SEC Filings,
as previously delivered to Lenders, correctly describe the principal properties
of the Company and the general nature of the business conducted by the Company.

                 SECTION 5.18 -- UCC Location.  The Company maintains is Chief
Executive Office and principal place of business is located at 100 Hartsfield
Centre Parkway, Suite 800, Atlanta, Georgia 30354-1356".

         7.      The following representation and warranty is hereby added as a
new Section 5.19:

                 "SECTION 5.19 -- Subject Reorganization.  Upon the
consummation of the Subject Reorganization, the Company shall be and remain in
compliance with all applicable provisions of this Agreement including without
limitation, those covenants contained in Section 6.02, 6.04, 6.05 and 6.06."

         8.      All representations and warranties contained under Article V
of the Credit Agreement solely as and only to the extent they pertain or apply
to Investments are hereby deleted.

         9.      Section 6.01 of the Credit Agreement is hereby amended by (i)
deleting Sections 6.01(i)(y) [in both places] and 6.01(i)(z) [in both places],
(ii) deleting Sections 6.01(ii)(y) [in both places] and 6.01(ii)(z) [in both
places], (iii) deleting the phrase "and Investments" as it appears in
6.01(iii)(a), (iv) deleting 6.01(iii)(a)(y), (v) deleting the phrase
"Investments, and immediately upon the filing of any one or more actions or
proceedings against" as it appears in Section 6.01(vii) and (vi) adding the
following phrase after the word "Company" as it appears in Section 6.01 (iv):

              "or any parent or holding company of the Company"



                                      5

                                        
<PAGE>   7

         10.     Section 6.02 of the Credit Agreement is hereby amended and
restated in its entirety to read follows:

                 "SECTION 6.02 -- [*]

         11.     Section 6.03 of the Credit Agreement is hereby deleted in its
entirety and such Section is hereby reserved for future use.

         12.     Sections 6.04, 6.05 and 6.06 are hereby amended in their
                 entirety to read as follows:


                 "SECTION 6.04 -- [*]

                 SECTION 6.05 -- [*]

                 SECTION 6.06 -- [*]

         13.     Section 6.14 of the Credit Agreement is hereby deleted in its
entirety and such Section is hereby reserved for future use.


         14.     Sections 7.01 through 7.04 are hereby amended and restated in
                 their entirety to read as follows:

                 "SECTION 7.01 -- [*]

                 SECTION 7.02 -- [*]

                 SECTION 7.03 -- [*]

                 SECTION 7.04 -- [*]

         15.     Section 7.06 is hereby amended and restated in its entirety to
                 read as follows:

                 "SECTION 7.06 -- [*]

         16.     Sections 7.07 and 7.08 of the Credit Agreement are hereby
deleted in their entirety and such Sections are hereby reserved for future use.

         17.     Sections 9.01(a)(i), 9.01(a)(ii), 9.01(a)(iii), 9.01(a)(iv),
and 9.01(a)(ix) of the Credit Agreement are hereby amended to delete the phrase
"or Investments" where included therein.



                                      6

                                        
<PAGE>   8


         18.     Section 9.01(a)(viii) of the Credit Agreement is hereby
amended to replace the reference to [*] with [*].

         19.     Section 9.01(a)(x) of the Credit Agreement is hereby amended
to delete the phrase "or the Guaranty," where the same is located therein.

         20.     Section 9.01(b) of the Credit Agreement is hereby amended to
delete the phrase "and Investments" in the three places such phrase appears
therein.

         21.     Section 11.01 of the Credit Agreement is hereby amended so as
to delete the phrases "the Guaranty" and "or Investments" in the two places
each such respective phrase appears therein.

         22.     Section 11.03 of the Credit Agreement is hereby amended so as
to delete the phrases "the Guaranty" and "and Investments" in each and every
place either such respective phrase appears therein.

         23.     Section 11.04 of the Credit Agreement is hereby amended so as
to delete the phrase "Investments," in the one place such phrase appears
therein.

         24.     Section 11.05 of the Credit Agreement is hereby amended so as
to delete the phrase "and Investments" in the two places such phrase appears
therein.

         25.     Section 11.09 of the Credit Agreement is hereby amended so as
to delete the phrase " or Investments" in the one place such phrase appears
therein.

         26.     Section 11.10 of the Credit Agreement is hereby amended so as
to delete (i) the phrases "or Investments" and "and Investments" and (ii) the
word "Investments" in the one place each such respective phrase or word appears
therein.

         27.     Section 11.12 of the Credit Agreement is hereby deleted in its
                 entirety.

         28.     Each of the undersigned Lenders represents and warrants to the
Company that such undersigned Lender has all requisite power and authority to
execute this Fourth Amendment which shall, upon execution by all of the
undersigned Lenders, constitute the legally binding obligation of all parties
to the Credit Agreement other than the Company and Investments.

         29.     The undersigned Lenders hereby consent to the implementation
and consummation of the Subject Reorganization (as defined in this Fourth
Amendment) by the Company and Investments and hereby waive (i) the Company's
and Investment's compliance with any other provisions contained under the
Credit Agreement or any other Basic Document which are deemed, interpreted or
construed to prohibit, prevent or restrict the Company's and Investment's
undertaking of the Subject Reorganization or (ii) any default or breach of any
provision of either




                                      7
                                        
<PAGE>   9


the Credit Agreement or any Basic Document resulting solely from the
implementation and consummation of the Subject Reorganization by the Company
and Investments provided, that nothing contained under subclause (ii) hereof
shall be deemed, interpreted or construed to constitute a waiver by any Lender
of any default or breach committed by the Company under the Credit Agreement or
any Basic Document (as amended hereby) from and after the consummation of the
Subject Reorganization.


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

ASA Investments, Inc                                 Atlantic Southeast
Airlines, Inc.                      
                                    
                                    
<TABLE>       
<S>                                       <C>                                                                     
By: /s/ Ronald V. Sapp                    By: /s/ Ronald V. Sapp                                                  
    --------------------------------          ------------------------------------------                         
    Title: Treasurer                          Title: Vice President-Finance                                     
                                                                                                                  
                                                                                                                  
                                                                                                                  
Bank of America Illinois                  Manufacturers Hanover Leasing International                             
                                          Corp., as Agent and as a Lender                                         
                                                                                                                  
                                                                                                                  
By: /s/ Patrick Horan                     By: /s/ Joseph D. Mellon,                                               
    --------------------------------          ------------------------------------------                          
    Title:Senior Vice President               Title:Attorney-in-Fact                                              
                                                                                                                  
                                                                                                                  
NationsBank, N.A. (South)                 National Bank of Canada.                                                
f/k/a NationsBank of Georgia, N.A.                                                                                
                                                                                                                  
                                                                                                                  
By: /s/ Kathryn W. Robinson               By: /s/ William L. Berry                                                
    --------------------------------          ------------------------------------------                          
    Title: Senior Vice President              Title: Vice President                                               
                                                                                                                  
                                                                                                                  
The Royal Bank of Canada                  Canadian Imperial Bank of Commerce                                      
                                                                                                                  
                                                                                                                  
By: /s/ Don Calancie                      By: /s/ Roger Colden                                                    
    --------------------------------          ------------------------------------------                          
    Title; Senior Manager                 Title: Authorized Signatory                                             
                                                                                                                  
                                                                                                                  
SouthTrust Bank of Georgia, N.A.          Kawasaki Leasing, (USA) Inc                                             
</TABLE> 



                                      8

                                        
<PAGE>   10


<TABLE>
<S>                                                  <C>
By: /s/ Ron Fontenot                                  By: /s/ Shigeru Inada                                               
    ---------------------------------------               ---------------------------------------
    Title: Vice President                                 Title: President
</TABLE>