<PAGE>
                                                                   EXHIBIT 10.23


                               FLEET NATIONAL BANK
                               100 Federal Street
                           Boston, Massachusetts 02110


                            As of September 30, 2001

Mercury Air Group, Inc.
5456 McConnell
Los Angeles, CA 90066

Attn: Randolf E. Ajer, Chief Financial Officer

        Re: Limited Consent

Ladies and Gentlemen:

        Reference is made to the Revolving Credit and Term Loan Agreement dated
as of March 2, 1999 (as amended, modified, supplemented or restated and in
effect from time to time, the "Credit Agreement") by and among (a) MERCURY AIR
GROUP, INC., a Delaware corporation having its principal place of business at
5456 McConnell Avenue, Los Angeles, California 90066 (the "Borrower"), (b) FLEET
NATIONAL BANK (formerly known as BankBoston, N.A.), a national banking
association, as agent (in such capacity the "Agent") for itself and the other
Banks referred to below; and (c) FLEET NATIONAL BANK and the other financial
institutions from time to time parties thereto (collectively, the "Banks").
Capitalized terms defined in the Credit Agreement that are not otherwise defined
in this letter agreement shall have the respective meanings assigned to such
terms in the Credit Agreement.

        Pursuant to Section 13.17 of the Credit Agreement, the Borrower has
agreed that it will not amend, supplement or otherwise modify the Subordinated
Debt Documents without the prior written consent of the Agent and the Majority
Banks. The Borrower has advised the the Agent that the Borrower and WMF have
agreed, inter alia, to amend certain financial covenants contained in the
Securities Purchase Agreement, dated as of September 10, 1999 (the "Purchase
Agreement") between the Borrower and WMF pursuant to the terms of an Amendment
No. 2 to the Purchase Agreement (the "Amendment") attached hereto as Exhibit A.

        Subject to the satisfaction of the conditions set forth below, the Agent
and the Majority Banks hereby consent to the amendment of the Subordinated Debt
Documents in accordance with the provisions contained in the Amendment.

        The limited consent set forth in this letter agreement shall be
effective upon the satisfaction of each of the following conditions, each to be
in form and substance satisfactory to the Agent:

                  (i) delivery to the Agent of original counterpart signature
        pages to this letter agreement, duly executed and delivered by the
        Majority Banks, the Borrower and each of the Guarantors;

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                                      -2-



                  (ii) receipt by the Agent, for the benefit of those Banks who
        execute and deliver a copy of this letter agreement by November 16, 2001
        (the "Signatory Banks"), a fee in the amount of $10,000 per Signatory
        Bank, as well as such fees payable to the Agent for its own account as
        may be agreed between the Borrower and the Agent; and

                  (iii) delivery to the Agent of a copy of the Amendment,
        including all schedules and exhibits thereto, certified by an officer of
        the Borrower as a true, correct and complete copy thereof.

        The consent contained in this letter agreement is limited strictly to
its terms, shall apply only to the specific matters and events described herein,
shall not extend to or affect any of the Borrower's or the Guarantors' other
obligations contained in the Credit Agreement or any other Loan Document. Except
as expressly set forth herein, nothing contained herein shall be deemed to be a
waiver of, or shall in any way impair or prejudice, any rights of the Agent or
the Banks under the Credit Agreement or any other Loan Document. Nothing
contained in this letter agreement shall be construed to imply a willingness on
the part of the Agent and the Banks to grant any similar or other future
consents.

        This letter agreement may be executed in any number of counterparts,
each of which when so executed shall be deemed to be an original and all of
which taken together shall constitute one and the same instrument. THIS LETTER
AGREEMENT SHALL BE AN INSTRUMENT UNDER SEAL AND SHALL BE GOVERNED BY, AND
CONSTRUED IN ACCORDANCE WITH, THE LAWS OF THE COMMONWEALTH OF MASSACHUSETTS
(WITHOUT REFERENCE TO PRINCIPLES OF CONFLICTS OR CHOICE OF LAW).

                [remainder of this page intentionally left blank]

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                                      -3-



        Kindly acknowledge your agreement with the terms of this letter
agreement by signing in the space indicated below and returning a copy of this
letter to the Agent.

                                        FLEET NATIONAL BANK
                                        (f/k/a BankBoston, N.A.),
                                        individually and as Agent


                                        By:
                                           -------------------------------------
                                           Name:
                                           Title:



                                        UNITED CALIFORNIA BANK
                                        FORMERLY KNOWN AS SANWA BANK CALIFORNIA


                                        By:
                                           -------------------------------------
                                           Name:
                                           Title:



                                        MELLON BANK, N.A.


                                        By:
                                           -------------------------------------
                                           Name:
                                           Title:



                                        UNION BANK OF CALIFORNIA, N.A.


                                        By:
                                           -------------------------------------
                                           Name:
                                           Title:


ACCEPTED AND AGREED:

MERCURY AIR GROUP, INC.


By:
   -------------------------------
   Name:  Randolph E. Ajer
   Title: Chief  Financial Officer

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                                      -4-



Each of the Guarantors hereby consents to the terms of the foregoing letter
agreement, and each confirms its obligation to the Agent and the Banks under its
Guaranty.


                                       MERCFUEL, INC.



                                       By:
                                          --------------------------------------
                                           Name:  John Condie
                                           Title:  Chief Financial Officer

                                       MAYTAG AIRCRAFT CORPORATION



                                       By:
                                          --------------------------------------
                                          Name:   Randolph E. Ajer
                                          Title:  Treasurer

                                       MERCURY AIR CARGO, INC.



                                       By:
                                          --------------------------------------
                                          Name:  Randolph E. Ajer
                                          Title:   Treasurer

                                       MERCURY ACCEPTANCE CORPORATION



                                       By:
                                          --------------------------------------
                                          Name:  Randolph E. Ajer
                                          Title:  Treasurer

                                       EXCEL CARGO, INC.



                                       By:
                                          --------------------------------------
                                          Name:  Randolph E. Ajer
                                          Title:  Treasurer

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                                      -5-



                                       MERCURY AIR CENTERS, INC.
                                       (f/k/a Wofford Flying Service, Inc.)



                                       By:
                                          --------------------------------------
                                          Name:  Randolph E. Ajer
                                          Title:  Treasurer


                                       AEG FINANCE CORPORATION



                                       By:
                                          --------------------------------------
                                          Name:  Randolph E. Ajer
                                          Title:   Treasurer


                                       JUPITER AIRLINE AUTOMATION
                                       SERVICES, INC.
                                       (f/k/a RPA Airline Automation Services,
                                       Inc. and Rene Perez and Associates, Inc.)



                                       By:
                                          --------------------------------------
                                          Name:  Randolph E. Ajer
                                          Title:  Treasurer


                                       HERMES AVIATION, INC.



                                       By:
                                          --------------------------------------
                                          Name:  Randolph E. Ajer
                                          Title:   Treasurer


                                       VULCAN AVIATION, INC.



                                       By:
                                          --------------------------------------
                                          Name:  Randolph E. Ajer
                                          Title:  Treasurer