<PAGE>

                                                                    EXHIBIT 10.4


                              AMENDED AND RESTATED

                     WMF SENIOR SUBORDINATED PROMISSORY NOTE


            THIS NOTE HAS NOT BEEN REGISTERED UNDER THE SECURITIES
            ACT OF 1933, AS AMENDED, OR THE SECURITIES LAWS OF ANY
            STATE AND MAY NOT BE SOLD, TRANSFERRED, OR OTHERWISE
            DISPOSED OF EXCEPT PURSUANT TO AN EFFECTIVE REGISTRATION
            STATEMENT UNDER SUCH ACT AND APPLICABLE STATE SECURITIES
            LAWS OR PURSUANT TO AN APPLICABLE EXEMPTION FROM THE
            REGISTRATION REQUIREMENTS OF SUCH ACT AND SUCH LAWS.


            THIS NOTE AND THE INDEBTEDNESS EVIDENCED HEREBY IS
            SUBORDINATE IN THE MANNER AND TO THE EXTENT SET FORTH IN
            THAT CERTAIN SUBORDINATION AGREEMENT, DATED AS OF
            DECEMBER 30, 2002, BY AND AMONG THE MAKER HEREOF, THE
            PAYEE NAMED HEREIN, AND FOOTHILL CAPITAL CORPORATION, AS
            SUCH AGREEMENT MAY BE AMENDED FROM TIME TO TIME, AND
            EACH HOLDER OF THIS NOTE, BY ITS ACCEPTANCE HEREOF,
            SHALL BE BOUND BY THE PROVISIONS OF SUCH SUBORDINATION
            AGREEMENT.

                             MERCURY AIR GROUP, INC.

                     12% SENIOR SUBORDINATED PROMISSORY NOTE
                              DUE December 31, 2005

$24,000,000                                                 New York, New York
                                                            September 10, 1999

            FOR VALUE RECEIVED, the undersigned, MERCURY AIR GROUP, INC., a
corporation organized under the laws of Delaware (the "Borrower"), hereby
promises to pay to the order of J.H. WHITNEY MEZZANINE FUND, L.P. ("WMF"), a
Delaware limited partnership, or its registered assigns (the "Holder"), the
principal sum of Twenty Four Million Dollars ($24,000,000) on December 31, 2005
(the "Maturity Date"), with interest thereon from time to time as provided
herein.

            1. Purchase Agreement. This Senior Subordinated Promissory Note (the
"Note") is issued by the Borrower, on the date hereof, pursuant to the
Securities Purchase Agreement (the "Purchase Agreement"), dated as of September
10, 1999, as amended to date, by
<PAGE>
and between the Borrower and WMF, and is subject to the terms thereof. This
Note, together with all other promissory notes issued under the Purchase
Agreement, and all promissory notes issued pursuant to paragraph 12 hereof or
any provision of the Purchase Agreement are hereinafter referred to as the
"Notes." The Holder is entitled to the benefits of this Note and the Purchase
Agreement, as it relates to the Note, and may enforce the agreements of the
Borrower contained herein and therein and exercise the remedies provided for
hereby and thereby or otherwise available in respect hereto and thereto.
Capitalized terms used herein without definition are used herein with the
meanings ascribed to such terms in the Purchase Agreement.

            2. Interest. (a) Basic Interest. The Borrower promises to pay
interest on the principal amount of this Note at the rate of 12% per annum. The
Borrower shall pay accrued interest quarterly on each March 31, June 30,
September 30 and December 31 of each year or, if any such date shall not be a
Business Day, on the next succeeding Business Day to occur after such date (each
date upon which interest shall be so payable, an "Interest Payment Date"),
beginning on September 30, 1999. Interest on this Note shall be paid by wire
transfer of immediately available funds to an account at a bank designated in
writing by the Holder. In the absence of any such written designation, any such
Interest payment shall be deemed made on the date a check in the applicable
amount payable to the order of Holder is received by the Holder at its last
address as reflected in Borrower's note register; if no such address appears,
then to such Holder in care of the last address in such note register of any
predecessor holder of this Note (or its predecessor). In addition to cash
interest, during the period beginning on January 1, 2004 and ending on June 30,
2004, the interest rate on this Note shall increase by a rate of 1% per annum
for each month Interest in excess of 12% per annum shall accrue and be added to
principal, and shall not be payable in cash. This increase in interest rate
shall take effect on the last day of each month from January 31, 2004 through
June 30, 2004, inclusive. Interest on this Note shall accrue from and including
the date of issuance through and until repayment of the principal and payment of
all accrued interest in full. Interest shall accrue and be computed on the basis
of a 360-day year of twelve 30-day months.

                  (b) Default Rate of Interest. Notwithstanding the foregoing
provisions of this Section 2, but subject to applicable law, any overdue
principal of and overdue interest on this Note shall bear interest, payable on
demand in immediately available funds, for each day from the date payment
thereof was due to the date of actual payment, at a rate equal to the rate of
interest otherwise in effect pursuant to the first sentence of this Section 2
plus 2% per annum, and, upon and during the occurrence of an Event of Default
(as hereinafter defined), this Note shall bear interest, from the date of the
occurrence of such Event of Default until such Event of Default is cured or
waived, payable on demand in immediately available funds, at a rate equal to the
rate of interest otherwise in effect pursuant to the first sentence of this
Section 2 plus 2% per annum. Subject to applicable law, any interest that shall
accrue on overdue interest on this Note as provided in the preceding sentence
and shall not have been paid in full on or before the next Interest Payment Date
to occur after the Interest Payment Date on which the overdue interest became
due and payable shall itself be deemed to be overdue interest on this Note to
which the preceding sentence shall apply.

                  (c) Maximum Interest. The maximum interest payable on this
Note pursuant to paragraphs (a) and (b) above is 18% per annum.


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                  (d) No Usurious Interest. In the event that any interest rate
provided for herein shall be determined to be unlawful, such interest rate shall
be computed at the highest rate permitted by applicable law. Any payment by the
Borrower of any interest amount in excess of that permitted by law shall be
considered a mistake, with the excess being applied to the principal of this
Note without prepayment premium or penalty; if no such principal amount is
outstanding, such excess shall be returned to Borrower.

            3. Mandatory Prepayment.

                  (a) Public Offerings. Subject to the subordination provisions
of Section 7 hereof and the Subordination Agreement (as hereinafter defined),
upon the consummation of a Public Offering (as hereinafter defined), the
Borrower shall, at the election of the Holder, prepay the outstanding principal
amount of this Note at the redemption prices (the "Mandatory Redemption Price"),
set forth below (together with interest accrued thereon), immediately following
receipt by any of the Borrower, or any of its Subsidiaries of the proceeds of
such Public Offering. For the purposes hereof, "Public Offering" means the sale
by any of the Borrower, or any of its Subsidiaries of its equity securities
(other than (i) stock options or warrants to acquire Common Stock awarded to
employees and directors pursuant to incentive compensation plans or agreements
with such Persons in an aggregate amount for all such options and warrants not
to exceed $250,000 per annum, and (ii) stock issued to a seller party to, and as
consideration for a Permitted Acquisition) pursuant to a registration statement
(other than on Form S-4 or S-8) or otherwise under the Securities Act, including
without limitation any offering which contemplates resale of the securities
issued under Rule144A under the Securities Act, in which the issuer receives any
Net Cash Proceeds. For the purposes hereof, "Net Cash Proceeds" means (x) the
cash proceeds in respect of a Public Offering minus (y) all costs of sale,
underwriting or brokerage costs and taxes paid or payable as a result thereof by
the Borrower or any of its Subsidiaries. The foregoing notwithstanding, until
all Senior Indebtedness to which this Note is subordinated shall be paid in
full, the amount of Net Proceeds which the Borrower shall be obligated to pay
under this Section 3(a) to the Holder as a prepayment of this Note at the
election of the Holder, shall be limited as set forth in the Subordination
Agreement. No penalty or premium shall apply to a prepayment made in accordance
with this paragraph




                  (b) Change of Control. Subject to the subordination provisions
of Section 7 hereof and the Subordination Agreement, upon the occurrence of a
Change of Control (as hereinafter defined), the Borrower shall, at the election
of the Holder, prepay the outstanding principal amount of this Note in
accordance with the Mandatory Redemption Prices set forth in Section 3(a) above
(together with interest accrued thereon), within 5 Business Days after the


                                     - 3 -
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occurrence of such Change of Control. For the purposes hereof, "Change of
Control" means (i) any transaction or series of transactions in which any Person
or group, other than WMF, CFK Partners or any of their respective affiliates
becomes the beneficial owner of 35% or more of the then outstanding capital
stock of the Borrower or of any of its Subsidiaries, the operations of which
would constitute a material part of the business or operations of the Borrower
and all of its Subsidiaries, taken as a whole, (ii) the sale of all or
substantially all of the assets of the Borrower or of any of its Subsidiaries,
the operations of which would constitute a material part of the business or
operations of the Borrower and all of its Subsidiaries, taken as a whole, (iii)
the liquidation of the Borrower or any of its Subsidiaries, the operations of
which would constitute a material part of the business or operations of the
Borrower and all of its Subsidiaries, taken as a whole, other than transactions
defined as Permitted Financing Transactions in, and entered into in compliance
with, the Purchase Agreement, and/or (iv) the combination of the Borrower or of
any of its Subsidiaries, the operations of which would constitute a material
part of the business or operations of the Borrower and all of its Subsidiaries,
taken as a whole, with another entity, as a result of which (A) any Person or
group, other WMF, CFK Partners or any of their respective affiliates becomes the
beneficial owner of 35% or more of the then outstanding capital stock of the
combined entity or (B) the directors of the Borrower or such Subsidiary, as the
case may be, constitute less than a majority of the Board of Directors of the
combined entity.

                  (c) Notice. The Borrower shall give written notice to the
Holder of any mandatory prepayment pursuant to this Section 3 at least five (5)
Business Days prior to the date of such prepayment. Such notice shall be given
in the manner specified in Section 11.2 of the Purchase Agreement.

            4. Optional Prepayment.

                  (a) Upon notice given to the Holder as provided in Section
4(b), the Borrower, at its option, may, at any time prepay all or any portion of
the principal amount of this Note at any time, by paying to the Holder an amount
equal to the principal amount to be repaid together with interest accrued and
unpaid thereon to the date fixed for such prepayment, and reasonable
out-of-pocket costs and expenses (including, without limitation, reasonable
fees, charges and disbursements of counsel), if any, associated with such
prepayment; provided, however, each prepayment of less than the full outstanding
balance of the principal amount of this Note shall be in an aggregate principal
amount of this Note of $1,000,000 or integral multiples of $100,000 in excess
thereof, and provided, further, that unless this Note and all Notes shall be
paid in full, the aggregate principal balance of the Notes outstanding at any
time shall be at least $500,000. No prepayment penalty or premium shall apply in
respect of any optional prepayment made in accordance with this paragraph.(b)
The Borrower may give written notice of prepayment of this Note or any portion
thereof not less than 10 nor more than 60 days prior to the date fixed for such
prepayment. Such notice of prepayment shall be given in the manner specified in
Section 11.2 of the Purchase Agreement. Upon notice of prepayment being given by
the Borrower, the Borrower covenants and agrees that it will prepay, on the date
therein fixed for prepayment, this Note or the portion hereof so called for
prepayment, at the outstanding principal amount thereof or the portion thereof
so called for prepayment, together with interest accrued and unpaid thereon to
the date fixed for such prepayment, together with the costs and expenses
referred to in Section 4(a).


                                     - 4 -
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                  (c) All optional prepayments under this Section 4 shall
include payment of accrued interest on the principal amount so prepaid and shall
be applied first to all costs, expenses and indemnities payable under the
Purchase Agreement, then to payment of default interest, if any, then to payment
of accrued interest, and thereafter to principal.

            5. Amendment. Amendments and modifications of this Note may be made
only in the manner provided in Section 11.4 of the Purchase Agreement.

            6. Defaults and Remedies.

                  (a) Events of Default. An "Event of Default" shall occur if:

            (i)   the Borrower shall default in the payment of the principal of
                  this Note, when and as the same shall become due and payable,
                  whether at maturity or at a date fixed for prepayment or by
                  acceleration or otherwise; or

            (ii)  the Borrower shall default in the payment of any installment
                  of interest on this Note according to its terms, when and as
                  the same shall become due and payable and such default shall
                  continue for a period of 5 days; or

            (iii) the Borrower shall default in the due observance or
                  performance of any covenant to be observed or performed
                  pursuant to Sections 8.1, 8.2(a), 8.3, 8.7, 8.8, 8.10, 8.11 or
                  Article 9 of the Purchase Agreement, and provided, however,
                  that a default under Article 9 which does not or is not likely
                  to have a material adverse effect on the Condition of the
                  Company shall become an Event of Default only if such default
                  shall continue for a period of 10 days; or

            (iv)  the Borrower or any of its Subsidiaries shall default in the
                  due observance or performance of any other covenant, condition
                  or agreement on the part of the Borrower or any of its
                  Subsidiaries to be observed or performed pursuant to the terms
                  hereof or pursuant to the terms of the Purchase Agreement or
                  any of the Transaction Documents (other than those referred to
                  in clauses (i), (ii) or (iii) of this Section 6(a)), and such
                  default shall continue for 30 days after the earliest of (A)
                  the date the Borrower is required pursuant to the Transaction
                  Documents or otherwise to give notice thereof to the Holder
                  (whether or not such notice is actually given) or (B) the date
                  of written notice thereof, specifying such default and, if
                  such default is capable of being remedied, requesting that the
                  same be remedied, shall have been given to the Borrower by the
                  Holder; or

            (v)   any representation, warranty or certification made by or on
                  behalf of the Borrower or any of its Subsidiaries in the
                  Purchase Agreement, this Note, the Transaction Documents or in
                  any certificate or other document delivered pursuant hereto or
                  thereto shall have been incorrect when made; or


                                     - 5 -
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            (vi)  any event or condition shall occur that results in the
                  acceleration of the maturity of any Indebtedness of the
                  Borrower or any of its Subsidiaries, in a principal amount
                  aggregating $100,000 or more; or

            (vii) an involuntary proceeding shall be commenced or an involuntary
                  petition shall be filed in a court of competent jurisdiction
                  seeking (a) relief in respect of the Borrower or any of its
                  Subsidiaries, or of a substantial part of its property or
                  assets, under Title 11 of the United States Code, as now
                  constituted or hereafter amended, or any other Federal or
                  state bankruptcy, insolvency, receivership or similar law, (b)
                  the appointment of a receiver, trustee, custodian,
                  sequestrator, conservator or similar official for the Borrower
                  or any of its Subsidiaries, or for a substantial part of its
                  property or assets, or (c) the winding up or liquidation of
                  the Borrower or any Subsidiary; and such proceeding or
                  petition shall continue undismissed for 60 days, or an order
                  or decree approving or ordering any of the foregoing shall be
                  entered; or

            (viii) the Borrower or any of its Subsidiaries shall (a) voluntarily
                  commence any proceeding or file any petition seeking relief
                  under Title 11 of the United States Code, as now constituted
                  or hereafter amended, or any other Federal or state
                  bankruptcy, insolvency, receivership or similar law, (b)
                  consent to the institution of, or fail to contest in a timely
                  and appropriate manner, any proceeding or the filing of any
                  petition described in paragraph (vii) of this Section 6(a),
                  (c) apply for or consent to the appointment of a receiver,
                  trustee, custodian, sequestrator, conservator or similar
                  official for the Borrower or any of its Subsidiaries, or for a
                  substantial part of their property or assets, (d) file an
                  answer admitting the material allegations of a petition filed
                  against it in any such proceeding, (e) make a general
                  assignment for the benefit of creditors, (f) become unable,
                  admit in writing its inability or fail generally to pay its
                  debts as they become due or (g) take any action for the
                  purpose of effecting any of the foregoing; or

            (ix)  one or more judgments for the payment of money in an aggregate
                  amount in excess of $500,000 (to the extent not covered by
                  insurance) shall be rendered against the Borrower or any of
                  its Subsidiaries and the same shall remain undischarged for a
                  period of 30 days during which execution shall not be
                  effectively stayed, or any action shall be legally taken by a
                  judgment creditor to levy upon assets or properties of the
                  Borrower or any of its Subsidiaries to enforce any such
                  judgment.

      (b)   Acceleration. If an Event of Default occurs under Section 6(a)(vii)
            or (viii), then the outstanding principal of and all accrued
            interest on this Note shall automatically become immediately due and
            payable, without presentment, demand, protest or notice of any kind,
            all of which are hereby expressly waived. If any other Event of
            Default occurs and is continuing, other than a default under Section
            8.7 of the Purchase Agreement, the Holder, by written notice to the


                                     - 6 -
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            Borrower, may declare the principal of and accrued interest on this
            Note to be immediately due and payable. Upon such declaration, such
            principal and interest shall become immediately due and payable. The
            Holder may rescind an acceleration and its consequences if all
            existing Events of Default have been cured or waived, except
            nonpayment of principal or interest that has become due solely
            because of the acceleration, and if the rescission would not
            conflict with any judgment or decree. Any notice or rescission shall
            be given in the manner specified in Section 11.2 of the Purchase
            Agreement. If any Event of Default occurs under Section 8.7 of the
            Purchase Agreement related to the failure to prepay amounts required
            on or prior to December 31, 2003, then, unless Borrower fails to
            take the remedial action set forth in such Section 8.7, Holder may
            not accelerate this Note or declare the full amount of principal
            then due and payable. Nothing in the preceding sentence shall impair
            any other remedy available to Holder as a result of such Event of
            Default (including the right to charge interest at the Default Rate,
            or the right to accelerate this Note upon Borrower's failure to
            issue Additional Notes or Additional Warrants or to prepay principal
            as agreed on or before December 31, 2004).

7. Subordination. Subject to the limitations set forth in Section 7(p) below,
this Note shall at all times be wholly subordinate and junior in right of
payment to all Senior Indebtedness to the extent and in the manner provided in
this Section 7.

      (a)   Definitions. As used in this Section 7, the following terms shall
            have the following meanings:

            "Indebtedness" shall have the meaning assigned to that term in the
Purchase Agreement.

            "Senior Covenant Default" shall mean any event of default as defined
under any agreement pertaining to Senior Indebtedness, other than a Senior
Payment Default.

            "Senior Credit Agreement" means the Senior Credit Agreement, as in
effect on the date hereof, by and among the Company, certain of its subsidiaries
and Foothill Capital Corporation.

            "Senior Indebtedness" has the meaning given to such term in the
Purchase Agreement.

            "Senior Default" shall mean a Senior Payment Default or a Senior
Covenant Default.

            "Senior Payment Default" shall mean any default in the payment of
any Senior Indebtedness.

            "Subordinated Indebtedness" shall mean (i) the principal of and
interest on this Note; (ii) any other obligations of the Borrower arising out of
or in connection with the Purchase Agreement, this Note or the other Transaction
Documents and (iii) any obligations of any of


                                     - 7 -
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Borrower's Subsidiaries arising out of or in connection with the Guaranties or
the other Transaction Documents.

      (b)   General. Upon the maturity of any Senior Indebtedness by lapse of
            time, acceleration, required prepayment or otherwise, all Senior
            Indebtedness shall first be paid in full, or such payment duly
            provided for in cash or in a manner satisfactory to the holders of
            such Senior Indebtedness, before any payment is made on account of
            the Subordinated Indebtedness or by the Borrower or Affiliates of
            the Borrower to acquire this Note. Notwithstanding any provision in
            Section 7 of this Note to the contrary, (i) for so long as no Senior
            Default has occurred and is continuing, or would occur as a result
            of such a payment, the Borrower may pay and the Holder may receive
            (A) all regularly scheduled payments of interest under this Note,
            and (B) all amounts due to the Holder or its Affiliates pursuant to
            either Section 2.4 or Section 7.1 of the Purchase Agreement, (ii)
            for so long as no Senior Default has occurred and is continuing or
            would occur as a result of any such prepayment, Borrower may prepay
            this Note in accordance with the provisions of Section 3 hereof, and
            the Holder may receive such prepayments, (iii) for so long as no
            Senior Default has occurred and is continuing, or would occur as a
            result of such a payment, the Borrower may prepay this Note in
            accordance with the provisions of Section 4 hereof and the Holder
            may receive such prepayments, and (iv) the Holder may receive any
            distributions provided for in Section 7(e)(ii) or 7(e)(iv) hereof.

      (c)   Limitation on Payment.

            (i)   Upon receipt by the Borrower and the Holder of a Blockage
                  Notice (as defined below), then unless and until (1) all
                  Senior Defaults that gave rise to the Blockage Notice shall
                  have been remedied or effectively waived or shall have ceased
                  to exist, or (2) the Senior Indebtedness in respect of which
                  such Senior Defaults shall have occurred shall have been paid
                  in full, no direct or indirect payment (in cash, property,
                  securities or by set-off or otherwise) of or on account of the
                  principal of or interest on this Note or as a sinking fund for
                  this Note or in respect of any redemption, retirement,
                  purchase or other acquisition of this Note shall be made
                  during any period prior to the expiration of the Blockage
                  Period (as defined below). Notwithstanding the foregoing, all
                  interest paid with respect to this Note prior to the receipt
                  of the Blockage Notice in question by the Holder hereof may be
                  kept by such Holder.

            (ii)  For purposes of this Section 7, a "Blockage Notice" is a
                  notice of a Senior Default that in fact has occurred and is
                  continuing, given to the Borrower and the Holder by the
                  holders of a majority in principal amount of the Senior
                  Indebtedness then outstanding (or their authorized agent);
                  provided, however, that no such notice shall be effective as a
                  Blockage Notice if an effective Blockage Notice shall have
                  been given within 360 days prior thereto.


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            (iii) For purposes of this Section 7, a "Blockage Period" with
                  respect to a Blockage Notice is the period commencing upon the
                  Borrower's receipt of such Blockage Notice and having a
                  duration as follows:

                        (1)   180 days if the Senior Default to which the
            Blockage Notice refers is a Senior Payment Default; or

                        (2)   90 days if the Senior Default to which the
            Blockage Notice refers is a Senior Covenant Default.

Notwithstanding any provision contained herein to the contrary: (A) the Borrower
shall not be prohibited from making, and the Holder shall not be prohibited from
receiving, payments under this Note pursuant to Section 7(c)(iii)(2) hereof for
more than an aggregate of 180 days within any 360 day period, (B) there shall
not be more than two Blockage Notices given in any 365 day period; (C) no Senior
Covenant Default existing on the date any Blockage Notice is given to the Holder
shall be used as a basis for any subsequent such notice, unless such Senior
Covenant Default shall have ceased to exist for a period of at least 180
consecutive days; and (D) once all Senior Defaults which gave rise to the
Blockage Notice in question shall have been remedied or effectively waived or
shall have ceased to exist, or the Senior Indebtedness in respect of which such
Senior Defaults shall have occurred shall have been paid in full, thereafter
(unless another Blockage Period shall then be in effect) all amounts which would
have been payable hereunder but for the existence of the Blockage Period
effected by the Blockage Notice delivered with respect to the Senior Default in
question shall be payable in their entirety.

      (d)   Limitation on Remedies. As long as any Senior Indebtedness remains
            outstanding, upon the occurrence of an Event of Default under this
            Note, the Holder shall not, unless the holders of any Senior
            Indebtedness shall have caused such Senior Indebtedness to become
            due prior to its stated maturity or any Event of Default pursuant to
            Section 6(a)(vii) or (viii) of this Note shall have commenced,
            declare or join in any declaration of this Note to be due and
            payable by reason of such Event of Default or otherwise take any
            action against the Borrower (including, without limitation,
            commencing any legal action against the Borrower or filing or
            joining in the filing of any insolvency petition against the
            Borrower) prior to the expiration of 30 days after the written
            notice of the Holder's ability to accelerate on account of the
            occurrence of such Event of Default (a "Remedy Notice") shall have
            been given by the Holder to the Borrower and the holders of the
            Senior Indebtedness (a "Remedy Standstill Period"), provided, that
            such Remedy Standstill Period shall be extended to (i) 60 days from
            the date of such Remedy Notice if, at the time the Remedy Standstill
            Period would otherwise expire, there exists any Senior Covenant
            Default, or (ii) 90 days from the date of such Remedy Notice if, at
            the time the Remedy Standstill Period would otherwise expire, there
            exists any Senior Payment Default.

            Notwithstanding the foregoing, the Remedy Standstill Period shall be
inapplicable or cease to be effective if the holders of any Senior Indebtedness
shall have caused such Senior Indebtedness to become due prior to its stated
maturity or an Event of Default pursuant to Section 6(a)(vii) or (viii) shall
have occurred. In addition, any Remedy Standstill Period shall


                                     - 9 -
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cease to be effective if at any time during such period: (i) (A) substantial
assets of Borrower or any of its Subsidiaries are sold or otherwise disposed of
(other than to a Person which is either wholly owned by Borrower or a wholly
owned Subsidiary thereof) outside of the ordinary course of business, (B) an
agreement or other arrangement for such sale or disposition is entered into, or
(C) the Board of Directors of the Borrower or such subsidiary authorizes or
approves such agreement, arrangement, sale or disposition or (ii)(A) payment or
any distribution of any character, whether in cash, securities or other property
of Borrower or any of its Subsidiaries shall be made to or received by any
creditor outside the ordinary course of business on any Indebtedness which is on
the same level of priority with or junior and subordinate in right of payment to
this Note, (B) an agreement or other arrangement for such payment or
distribution is entered into, or (C) the Board of Directors of the Borrower or
such Subsidiary authorizes or approves such agreement, arrangement, payment or
distribution.

            Upon the expiration or termination of any Remedy Standstill Period,
the Holder shall be entitled to exercise any of its rights with respect to this
Note other than any right to accelerate the maturity date of this Note based
upon the occurrence of any Event of Default in respect thereto which has been
cured or otherwise remedied during the Remedy Period.

      (e)   Subordination Upon Certain Events. Upon the occurrence of any Event
            of Default with respect to under Sections 6(a)(vii) or (viii) of
            this Note:

            (i)   Upon any payment or distribution of assets of the Borrower to
                  creditors of the Borrower, holders of Senior Indebtedness
                  shall be entitled to receive indefeasible payment in full of
                  all obligations with respect to the Senior Indebtedness before
                  the Holder shall be entitled to receive any payment in respect
                  of the Subordinated Indebtedness.

            (ii)  Until all Senior Indebtedness is paid in full, any
                  distribution to which the Holder would be entitled but for
                  this Section 7 shall be made to the holders of Senior
                  Indebtedness, as their interests may appear, except that the
                  Holder may, pursuant to a plan of reorganization under Chapter
                  11 of the Bankruptcy Code of 1978, as amended, or any similar
                  provision of any successor legislation thereto, receive
                  securities that are subordinate to the Senior Indebtedness to
                  at least the same extent as this Note if pursuant to such plan
                  the distributions to the holders of the Senior Indebtedness in
                  the form of cash, securities or other property, by set-off or
                  otherwise, provide for payment of the full amount of the
                  allowed claim of the holders of the Senior Indebtedness.

            (iii) For purposes of this Section 7, a distribution may consist of
                  cash, securities or other property, by set-off or otherwise.

            (iv)  Notwithstanding the foregoing provisions of Section 7(b),(c)
                  or (e), if payment or delivery by the Borrower of cash,
                  securities or other property to the Holder is authorized by an
                  order or decree giving effect, and stating in such order or
                  decree that effect is given, to the subordination of this Note
                  to the Senior Indebtedness, and made by a court of competent


                                     - 10 -
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                  jurisdiction in a proceeding under any applicable bankruptcy
                  or reorganization law, payment or delivery by such Borrower of
                  such cash, securities or other property shall be made to the
                  Holder in accordance with such order or decree.

      (f)   Payments and Distributions Received. If the Holder shall have
            received any payment from or distribution of assets of the Borrower
            in respect of the Subordinated Indebtedness in contravention of the
            terms of this Section 7 before all Senior Indebtedness is paid in
            full, then and in such event such payment or distribution shall be
            received and held in trust for and shall be promptly paid over or
            delivered to the holders of Senior Indebtedness to the extent
            necessary to pay all such Senior Indebtedness in full.

      (g)   Proofs of Claim. If, while any Senior Indebtedness is outstanding,
            any Event of Default under Section 6(a)(vii) or (viii) of this Note
            occurs with respect to the Borrower, the Holder shall duly and
            promptly take such action as any holder of Senior Indebtedness may
            reasonably request to collect any payment with respect to this Note
            for the account of the holders of the Senior Indebtedness and to
            file appropriate claims or proofs of claim in respect of this Note.
            Upon the failure of the Holder to take any such action, each holder
            of Senior Indebtedness is hereby irrevocably authorized and
            empowered (in its own name or otherwise), but shall have no
            obligation, to demand, sue for, collect and receive every payment or
            distribution referred to in respect of this Note and to file claims
            and proofs of claim and take such other action as it may deem
            necessary or advisable for the exercise or enforcement of any of the
            rights or interests of the Holder with respect to this Note.

      (h)   Subrogation. After all amounts payable under or in respect of Senior
            Indebtedness are paid in full, the Holder shall be subrogated to the
            rights of holders of Senior Indebtedness to receive payments or
            distributions applicable to Senior Indebtedness to the extent that
            distributions otherwise payable to the Holder have been applied to
            the payment of Senior Indebtedness. A distribution made under this
            Section 7 to a holder of Senior Indebtedness which otherwise would
            have been made to the Holder is not, as between the Borrower and the
            Holder, a payment by the Borrower on Senior Indebtedness.

      (i)   Relative Rights. This Section defines the relative rights of the
            Holder and the holders of Senior Indebtedness. Nothing in this
            Section shall: (1) impair, as between the Borrower and the Holder,
            the obligations of the Borrower, which are absolute and
            unconditional, to pay principal of and interest (including default
            interest) on this Note in accordance with its terms; (2) affect the
            relative rights of the Holder and creditors of the Borrower other
            than holders of Senior Indebtedness or (3) prevent the Holder from
            exercising its available remedies upon a default or Event of
            Default, subject to the rights, if any, under this Section 7 of
            holders of Senior Indebtedness.


                                     - 11 -
<PAGE>
      (j)   Subordination May Not Be Impaired by the Borrower. No right of any
            holder of any Senior Indebtedness to enforce the subordination of
            the Indebtedness evidenced by this Note shall be impaired by any
            failure to act by the Borrower or such holder of Senior Indebtedness
            or by the failure of the Borrower or such holder to comply with this
            Note. The provisions of this Section 7 shall continue to be
            effective or be reinstated, as the case may be, if at any time any
            payment of any of the Senior Indebtedness is rescinded or must
            otherwise be returned by any holder of Senior Indebtedness as a
            result of the insolvency, bankruptcy or reorganization of the
            Borrower or any of its Subsidiaries or otherwise, all as though such
            payment had not been made.

      (k)   Payments. A payment with respect to principal of or interest on the
            Subordinated Indebtedness shall include, without limitation, payment
            of principal of, and interest on this Note, any depositing of funds
            for the defeasance of the Subordinated Indebtedness, any sinking
            fund and any payment on account of mandatory prepayment or optional
            prepayment provisions.

      (l)   Section Not to Prevent Events of Default. The failure to make a
            payment on account of principal of or interest on or other amounts
            constituting Subordinated Indebtedness by reason of any provision of
            this Section 7 shall not be construed as preventing the occurrence
            of an Event of Default under Section 6.

      (m)   Subordination Not Impaired: Benefit of Subordination. The Holder
            agrees and consents that without notice to or assent by such Holder,
            and without affecting the liabilities and obligations of the
            Borrower and the rights and benefits of the holders of the Senior
            Indebtedness set forth in this Section 7:

            (i)   The obligations and liabilities of the Borrower and any other
                  party or parties for or upon the Senior Indebtedness may, from
                  time to time, be increased, renewed, refinanced, extended,
                  modified, amended, restated, compromised, supplemented,
                  terminated, waived or released, except as prohibited by
                  Sections 9.3 and 9.4 of the Purchase Agreement;

            (ii)  The holders of Senior Indebtedness, and any representative or
                  representatives acting on behalf thereof, may exercise or
                  refrain from exercising any right, remedy or power granted by
                  or in connection with any agreements relating to the Senior
                  Indebtedness; and

            (iii) Any balance or balances of funds with any holder of Senior
                  Indebtedness at any time outstanding to the credit of the
                  Borrower may, from time to time, in whole or in part, be
                  surrendered or released;

all as the holders of the Senior Indebtedness, and any representative or
representatives acting on behalf thereof, may deem advisable, and all without
impairing, abridging, diminishing, releasing or affecting the subordination of
the Subordinated Indebtedness to the Senior Indebtedness provided for herein.


                                     - 12 -
<PAGE>
      (n)   Modification of Section 7. The provisions of this Section 7 are for
            the benefit of the holders from time to time of Senior Indebtedness
            and, so long as any Senior Indebtedness remains unpaid, may not be
            modified, rescinded or canceled in whole or in part without the
            prior written consent thereto of all holders of Senior Indebtedness.

      (o)   Covenants of Holder. Until all of the Senior Indebtedness has been
            fully paid:

            (i)   The Holder shall not hereafter give any subordination in
                  respect of this Note.

            (ii)  Upon the occurrence and during the continuance of a Senior
                  Default, the Holder shall not release, exchange, extend the
                  time of payment of, compromise, set off or otherwise discharge
                  any part of this Note or modify or amend this Note; provided,
                  however, that at such time or times as the actions referred to
                  in this Section 7(o)(ii) may be taken by the Holder, such
                  Holder shall give the holders of Senior Indebtedness five
                  Business Days prior written notice before taking any of such
                  actions.

            (iii) The Holder hereby undertakes and agrees for the benefit of the
                  holders of Senior Indebtedness that, upon the occurrence and
                  during the continuance of a Senior Default, it shall take any
                  actions reasonably requested by any holder of Senior
                  Indebtedness to effectuate the full benefit of the
                  subordination contained herein.

      (p)   Covenant of the Borrower, Limitation on Indebtedness. Until all
            Subordinated Indebtedness shall have been paid in full, the Borrower
            shall not, and shall not cause, suffer or permit any of its
            Subsidiaries to, directly or indirectly, collectively and in the
            aggregate, issue, assume or otherwise incur Senior Indebtedness or
            other Indebtedness except as permitted under Section 9.4 of the
            Purchase Agreement, as it now exists or may be amended or modified.

      (q)   Miscellaneous.

            (i)   To the extent permitted by applicable law, the Holder and the
                  Borrower hereby waive (1) notice of acceptance hereof by the
                  holders of the Senior Indebtedness, and (2) all diligence in
                  the collection or protection of or realization upon the Senior
                  Indebtedness.

            (ii)  The Borrower and the Holder hereby expressly agree that the
                  holders of Senior Indebtedness may enforce any and all rights
                  derived herein by suit, either in equity or law, for specific
                  performance of any agreement contained in this Section 7 or
                  for judgment at law and any other relief whatsoever
                  appropriate to such action or procedure.

            (iii) The Holder acknowledges and agrees that the foregoing
                  subordination provisions are, and are intended to be, an
                  inducement and a consideration to each holder of Senior
                  Indebtedness, whether such Senior Indebtedness


                                     - 13 -
<PAGE>
                  was created or acquired before or after the issuance of this
                  Agreement, and each holder of Senior Indebtedness shall be
                  deemed conclusively to have relied upon such subordination
                  provisions in acquiring and continuing to hold such Senior
                  Indebtedness.

      (r)   Subordination Agreement. Notwithstanding anything to the contrary
            contained in this Section 7, the terms and conditions of the
            Subordination Agreement dated the date hereof among WMF, the
            Borrower and Foothill Capital Corporation (the "Subordination
            Agreement") shall govern the subordination of the Subordinated
            Indebtedness as long as the Subordination Agreement remains in full
            force and effect.

8. Use of Proceeds. The Borrower shall use the principal amount of this Note in
accordance with the permitted uses described in Section 8.10 of the Purchase
Agreement.

9. Suits for Enforcement.

      (a)   Subject to Section 7, upon the occurrence of any one or more Events
            of Default, the Holder of this Note may proceed to protect and
            enforce its rights hereunder by suit in equity, action at law or by
            other appropriate proceeding, whether for the specific performance
            of any covenant or agreement contained in the Purchase Agreement or
            this Note or in aid of the exercise of any power granted in the
            Purchase Agreement or this Note, or may proceed to enforce the
            payment of this Note, or to enforce any other legal or equitable
            right of the Holders of this Note.

      (b)   In case of any default under this Note, the Borrower will pay to the
            Holder such amounts as shall be sufficient to cover the costs and
            expenses of such Holder due to such default, as provided in Article
            7 of the Purchase Agreement.

10. Remedies Cumulative. No remedy herein conferred upon the Holder is intended
to be exclusive of any other remedy and each and every such remedy shall be
cumulative and shall be in addition to every other remedy given hereunder or now
or hereafter existing at law or in equity or by statute or otherwise.

11. Remedies Not Waived. No course of dealing between the Borrower and the
Holder or any delay on the part of the Holder in exercising any rights hereunder
shall operate as a waiver of any right.

12. Transfer.

      (a)   The term "Holder" as used herein shall also include any transferee
            of this Note whose name has been recorded by the Borrower in the
            Note Register. Each transferee of this Note acknowledges that this
            Note has not been registered under the Securities Act, and may be
            transferred only pursuant to an effective registration under the
            Securities Act or pursuant to an applicable exemption from the
            registration requirements of the Securities Act.


                                     - 14 -
<PAGE>
      (b)   The Borrower shall maintain a register (the "Note Register") in its
            principal offices for the purpose of registering the Note and any
            transfer or partial transfer thereof, which register shall reflect
            and identify, at all times, the ownership of record of any interest
            in the Note. Upon the issuance of this Note, the Borrower shall
            record the name and address of the initial purchaser of this Note in
            the Note Register as the first Holder. Upon surrender for
            registration of transfer or exchange of this Note at the principal
            offices of the Borrower, the Borrower shall, at its expense, execute
            and deliver one or more new Notes of like tenor and of denominations
            of at least $500,000 (except as may be necessary to reflect any
            principal amount not evenly divisible by $500,000 of a like
            aggregate principal amount, registered in the name of the Holder or
            a transferee or transferees. Every Note surrendered for registration
            of transfer or exchange shall be duly endorsed, or be accompanied by
            written instrument of transfer duly executed by the Holder of such
            Note or such holder's attorney duly authorized in writing.

      (c)   This Note may be transferred or assigned, in whole or in part, by
            the Holder at any time.

13. Replacement of Note. On receipt by the Borrower of an affidavit of an
authorized representative of the Holder stating the circumstances of the loss,
theft, destruction or mutilation of this Note (and in the case of any such
mutilation, on surrender and cancellation of such Note), the Borrower, at its
expense, will promptly execute and deliver, in lieu thereof, a new Note of like
tenor. If required by the Borrower, such Holder must provide indemnity
sufficient in the reasonable judgment of the Borrower to protect the Borrower
from any loss which they may suffer if a lost, stolen or destroyed Note is
replaced.

14. Covenants Bind Successors and Assigns. All the covenants, stipulations,
promises and agreements in this Note contained by or on behalf of the Borrower
shall bind its successors and assigns, whether so expressed or not.

15. Notices. All notices, demands and other communications provided for or
permitted hereunder shall be made in writing and shall be by registered or
certified first-class mail, return receipt requested, telecopier (with receipt
confirmed), courier service or personal delivery at the addresses specified in
Section 11.2 of the Purchase Agreement. All such notices and communications
shall be deemed to have been duly given when: delivered by hand, if personally
delivered; when delivered by courier, if delivered by commercial overnight
courier service; if mailed, five Business Days after being deposited in the
mail, postage prepaid; or if telecopied, when receipt is acknowledged.

16. GOVERNING LAW. THIS NOTE SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE
WITH THE LAWS OF THE STATE OF NEW YORK WITHOUT REGARD TO THE PRINCIPLES OF
CONFLICTS OF LAW OF SUCH STATE (INCLUDING GIVING EFFECT TO GOL SECTION 5-1401).

17. Severability. If any one or more of the provisions contained herein, or the
application thereof in any circumstance, is held invalid, illegal or
unenforceable in any respect for any


                                     - 15 -
<PAGE>
reason, the validity, legality and enforceability of any such provision in every
other respect and of the remaining provisions hereof shall not be in any way
impaired, unless the provisions held







                                     - 16 -
<PAGE>
invalid, illegal or unenforceable shall substantially impair the benefits of
the remaining provisions hereof

18. Headings. The headings in this Note are for convenience of reference only
and shall not limit or otherwise affect the meaning hereof

                                    MERCURY AIR GROUP, INC.

                                    By: ____________________________
                                        Name:
                                        Title:



                                     - 17 -