<PAGE>   1
                                                                     EXHIBIT 4.3

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                           REVOLVING CREDIT AGREEMENT



                          Dated as of December 14, 2000


                                     between


                       STATE STREET BANK AND TRUST COMPANY
                      OF CONNECTICUT, NATIONAL ASSOCIATION,

                             as Subordination Agent,
                          as agent and trustee for the
                   United Airlines 2000-2B Pass Through Trust,

                                   as Borrower


                      WESTDEUTSCHE LANDESBANK GIROZENTRALE,
                                New York Branch,

                              as Liquidity Provider



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                                   Relating to

                   United Airlines 2000-2B Pass Through Trust
       United Airlines Enhanced Pass Through Certificates, Series 2000-2B


<PAGE>   2


                               TABLE OF CONTENTS


<TABLE>
                                                     ARTICLE I

                                                    DEFINITIONS
         <S>               <C>                                                                                   <C>
         Section 1.01      Certain Defined Terms................................................................  1

                                                    ARTICLE II

                                        AMOUNT AND TERMS OF THE COMMITMENT
         Section 2.01      Advances.............................................................................  7
         Section 2.02      Making the Advances..................................................................  7
         Section 2.03      Fees................................................................................. 10
         Section 2.04      Automatic Reductions and Termination of the Maximum Commitment
                            .................................................................................... 10
         Section 2.05      Repayments of Interest Advances or the Final Advance................................. 10
         Section 2.06      Repayments of Provider Advances...................................................... 10
         Section 2.07      Payments to the Liquidity Provider Under the Intercreditor Agreement................. 11
         Section 2.08      Book Entries......................................................................... 12
         Section 2.09      Payments from Available Funds Only................................................... 12
         Section 2.10      Extension of Expiry Date............................................................. 12

                                                    ARTICLE III

                                            OBLIGATIONS OF THE BORROWER
         Section 3.01      Increased Costs...................................................................... 13
         Section 3.02      Capital Adequacy..................................................................... 14
         Section 3.03      Payments Free of Deductions.......................................................... 14
         Section 3.04      Payments............................................................................. 15
         Section 3.05      Computations......................................................................... 16
         Section 3.06      Payment on Non-Business Days......................................................... 16
         Section 3.07      Interest............................................................................. 16
         Section 3.08      Replacement of Borrower.............................................................. 17
         Section 3.09      Funding Loss Indemnification......................................................... 18
         Section 3.10      Illegality........................................................................... 18

                                                    ARTICLE IV

                                               CONDITIONS PRECEDENT
         Section 4.01      Conditions Precedent to Effectiveness of Section 2.01................................ 18
</TABLE>


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<TABLE>
         <S>               <C>                                                                                   <C>
         Section 4.02      Conditions Precedent to Borrowing.................................................... 20

                                                     ARTICLE V

                                                     COVENANTS
         Section 5.01      Affirmative Covenants of the Borrower................................................ 20
         Section 5.02      Negative Covenants of the Borrower................................................... 21

                                                    ARTICLE VI

                                            LIQUIDITY EVENTS OF DEFAULT
         Section 6.01      Liquidity Events of Default.......................................................... 21

                                                    ARTICLE VII

                                                   MISCELLANEOUS
         Section 7.01      Amendments, Etc...................................................................... 21
         Section 7.02      Notices, Etc......................................................................... 22
         Section 7.03      No Waiver; Remedies.................................................................. 23
         Section 7.04      Further Assurances................................................................... 23
         Section 7.05      Indemnification; Survival of Certain Provisions...................................... 23
         Section 7.06      Liability of the Liquidity Provider.................................................. 23
         Section 7.07      Costs, Expenses and Taxes............................................................ 24
         Section 7.08      Binding Effect; Participations....................................................... 24
         Section 7.09      Severability......................................................................... 26
         Section 7.10      GOVERNING LAW........................................................................ 26
         Section 7.11      Submission to Jurisdiction; Waiver of Jury Trial; Waiver of Immunity ................ 26
         Section 7.12      Execution in Counterparts............................................................ 27
         Section 7.13      Entirety............................................................................. 27
         Section 7.14      Headings............................................................................. 27
         Section 7.15      LIQUIDITY PROVIDER'S OBLIGATION TO MAKE ADVANCES..................................... 28
</TABLE>

Annex I           Interest Advance Notice of Borrowing
Annex II          Non-Extension Advance Notice of Borrowing
Annex III         Downgrade Advance Notice of Borrowing
Annex IV          Final Advance Notice of Borrowing
Annex V           Notice of Termination
Annex VI          Notice of Replacement Subordination Agent


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                           REVOLVING CREDIT AGREEMENT

         This REVOLVING CREDIT AGREEMENT, dated as of December 14, 2000 (as it
may be amended, supplemented or otherwise modified from time to time in
accordance with the terms hereof, this "Agreement"), between STATE STREET BANK
AND TRUST COMPANY OF CONNECTICUT, NATIONAL ASSOCIATION, a national banking
association, not in its individual capacity but solely as Subordination Agent
under the Intercreditor Agreement (each as defined below), as agent and trustee
for the Class B Trust (as defined below) (the "Borrower"), and WESTDEUTSCHE
LANDESBANK GIROZENTRALE, a German banking institution organized under the laws
of the State of North Rhine - Westphalia, Germany, acting through its New York
branch ("West LB") ("Liquidity Provider").

                               W I T N E S S E T H

                  WHEREAS, pursuant to the Class B Trust Agreement (as defined
below), the Class B Trust is issuing the Class B Certificates; and

                  WHEREAS, the Borrower, in order to support the timely payment
of a portion of the interest on the Class B Certificates in accordance with
their terms, has requested the Liquidity Provider to enter into this Agreement,
providing in part for the Borrower to request in specified circumstances that
Advances be made hereunder.

                  NOW, THEREFORE, in consideration of the mutual promises
contained herein, and of other good and valuable consideration the receipt and
adequacy of which are hereby acknowledged, the parties hereto agree as follows:

                                    ARTICLE I

                                   DEFINITIONS

         Section 1.01      Certain Defined Terms. (a) For all purposes of this
Agreement, except as otherwise expressly provided or unless the context
otherwise requires:

                           (i)      the terms used herein that are defined in
         this Article I have the meanings assigned to them in this Article I,
         and include the plural as well as the singular;

                           (ii)     all references in this Agreement to
         designated "Articles," "Sections" and other subdivisions are to the
         designated Articles, Sections and other subdivisions of this Agreement;

                           (iii)    the words "herein," "hereof" and "hereunder"
         and other words of similar import refer to this Agreement as a whole
         and not to any particular Article, Section or other subdivision; and


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                                                    [REVOLVING CREDIT AGREEMENT]

                           (iv)     the term "including" means "including
         without limitation".

                  "Additional Costs" has the meaning specified in Section 3.01.

                  "Advance" means an Interest Advance, a Final Advance, a
Provider Advance or an Applied Provider Advance, as the case may be.

                  "Applicable Liquidity Rate" has the meaning specified in
Section 3.07(g).

                  "Applicable Margin" means, with respect to any Unpaid Advance
or Applied Provider Advance, 1.5%.

                  "Applied Downgrade Advance" has the meaning specified in
Section 2.06(a).

                  "Applied Non-Extension Advance" has the meaning assigned to
such term in Section 2.06(a).

                  "Applied Provider Advance" has the meaning assigned to such
term in Section 2.06(a).

                  "Base Rate" means a fluctuating interest rate per annum in
effect from time to time, which rate per annum shall at all times be equal to
the weighted average of the rates on overnight Federal funds transactions with
members of the Federal Reserve System arranged by Federal funds brokers, as
published for each day in the period for which the Base Rate is to be determined
(or, if such day is not a Business Day, for the preceding Business Day) by the
Federal Reserve Bank of New York, or if such rate is not so published for any
day that is a Business Day, the average of the quotations for such day for such
transactions received by the Liquidity Provider from three Federal funds brokers
of recognized standing selected by it, plus one-quarter of one percent (.25%).

                  "Base Rate Advance" means an Advance that bears interest at a
rate based upon the Base Rate.

                  "Borrower" has the meaning specified in the recitals to this
Agreement.

                  "Borrowing" means the making of Advances requested by delivery
of a Notice of Borrowing.

                  "Business Day" means any day (x) other than a Saturday or
Sunday or a day on which commercial banks are authorized or required by law to
close in Chicago, Illinois, New York, New York or the city and state in which
the Class B Trustee, the Subordination Agent or any Indenture Trustee maintains
its corporate trust office or receives and disburses funds, and


                                       2
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                                                    [REVOLVING CREDIT AGREEMENT]

(y) if the applicable Business Day relates to any Advance or amount bearing
interest based on LIBOR, on which dealings are carried on in the London
interbank market.

                  "Consent Period" has the meaning specified in Section 2.10.

                  "Downgrade Advance" means an Advance made pursuant to Section
2.02(c).

                  "Effective Date" has the meaning specified in Section 4.01.
The delivery of the certificate of the Liquidity Provider contemplated by
Section 4.01(e) shall be conclusive evidence that the Effective Date has
occurred.

                  "Excluded Taxes" means (i) any Taxes imposed on, based on, or
measured by the overall net income, capital, franchises, or receipts (other than
Taxes which are or are in the nature of sales or use Taxes or value added Taxes)
of the Liquidity Provider or any of its Lending Offices, (ii) withholding Taxes
imposed under laws in effect on the date hereof by the United States on payments
to a recipient in the jurisdiction in which the Liquidity Provider's initial
Lending Office is located, and (iii) withholding Taxes imposed by the United
States on payments to a recipient in any other jurisdiction to which such
Lending Office is moved if, under the laws in effect at the time of such move,
such laws would require greater withholding of Taxes on payments to such
Liquidity Provider acting from an office in such jurisdiction than would be
required on payments to such Liquidity Provider acting from an office in the
jurisdiction from which such Lending Office was moved.

                  "Expenses" means liabilities, obligations, damages,
settlements, penalties, claims, actions, suits, costs, expenses, and
disbursements (including, without limitation, reasonable fees and disbursements
of legal counsel and costs of investigation), provided that Expenses shall not
include Taxes.

                  "Expiry Date" means December 12, 2001, initially, or any date
to which the Expiry Date is extended pursuant to Section 2.10.

                  "Final Advance" means an Advance made pursuant to Section
2.02(d).

                  "Indenture Trustee" means, with respect to any Indenture, the
Indenture Trustee thereunder.

                  "Intercreditor Agreement" means the Intercreditor Agreement,
dated as of December 14, 2000 between the Trustee, the Liquidity Provider, the
liquidity provider under each Liquidity Facility (other than this Agreement) and
the Subordination Agent, as the same may be amended, supplemented or otherwise
modified from time to time in accordance with its terms.


                                       3
<PAGE>   7

                                                    [REVOLVING CREDIT AGREEMENT]

                  "Interest Advance" means an Advance made pursuant to Section
2.02(a).

                  "Interest Period" means, with respect to any LIBOR Advance,
each of the following periods:

                  (1)      the period beginning on the third Business Day
         following either (x) the Liquidity Provider's receipt of the Notice of
         Borrowing for such LIBOR Advance or (y) the withdrawal of funds from
         the Class B Cash Collateral Account for the purpose of paying interest
         on the Class B Certificates as contemplated by Section 2.06(a) hereof
         and, in either case, ending on the next Regular Distribution Date; and

                  (2)      each subsequent period commencing on the last day of
         the preceding Interest Period and ending on the next Regular
         Distribution Date;

provided, however, that if (x) the Final Advance shall have been made, or (y)
other outstanding Advances shall have been converted into the Final Advance,
then the Interest Periods shall be successive periods of one month beginning on
the third Business Day following the Liquidity Provider's receipt of the Notice
of Borrowing for such Final Advance (in the case of clause (x) above) or the
Regular Distribution Date following such conversion (in the case of clause (y)
above).

                  "Lending Office" means the lending office of the Liquidity
Provider, presently located at New York, New York, or such other lending office
as the Liquidity Provider from time to time shall notify the Borrower as its
lending office hereunder.

                  "LIBOR" means, with respect to any Interest Period, the
interest rate per annum at which deposits in United States dollars are offered
to prime banks in the London interbank market as indicated on display page 3750
(British Bankers Association-LIBOR) of the Dow Jones Markets Service (or such
other page as may replace such display page 3750 for the purpose of displaying
London interbank offered rates for United States dollar deposits) or, if not so
indicated, the average (rounded upwards to the nearest 1/16%), as determined by
the Liquidity Provider, of such rates as indicated on the Reuters Screen LIBO
Page (or such other page as may replace such Reuters Screen LIBO Page for the
purpose of displaying London interbank offered rates for United States dollar
deposits) or, if neither such alternative is indicated, the average (rounded
upwards to the nearest 1/16%), as determined by the Liquidity Provider, of such
rates offered by the London Reference Banks to prime banks in the London
interbank market, in each case at or about 11:00 a.m. (London time) on the day
two LIBOR Business Days prior to the first day of such Interest Period for
deposits of a duration equal to such Interest Period (or such other period most
nearly corresponding to such period) in an amount substantially equal to the
principal amount of the applicable LIBOR Advance as of the first day of such
Interest Period. The Liquidity Provider will, if necessary, request that each of
the London Reference Banks provide a quotation of its rate. If at least two such
quotations are provided, the rate will be the


                                       4
<PAGE>   8
                                                    [REVOLVING CREDIT AGREEMENT]

average of the quotations (rounded upwards to the nearest 1/100%). If no such
quotation can be obtained, the rate will be Base Rate.

                  "LIBOR Advance" means an Advance bearing interest at a rate
based upon LIBOR.

                  "Liquidity Event of Default" means the occurrence of either
(a) the Acceleration of all of the Equipment Notes or (b) a United Bankruptcy
Event.

                  "Liquidity Indemnitee" means (i) the Liquidity Provider, (ii)
the directors, officers, employees, servants and agents of the Liquidity
Provider, and (iii) the successors and permitted assigns of the persons
described in clauses (i) through (ii), inclusive.

                  "Liquidity Provider" has the meaning specified in the recital
of parties to this Agreement.

                  "London Reference Banks" means the principal London offices of
National Westminster Bank PLC, the Mitsubishi Trust and Banking Corporation and
ABN AMRO Bank N.V., or such other bank or banks as may from time to time be
agreed to by United and the Liquidity Provider.

                  "Maximum Available Commitment" shall mean, subject to the
proviso contained in the third sentence of Section 2.02(a), at any time of
determination, (a) the Maximum Commitment at such time, less (b) the aggregate
amount of each Interest Advance outstanding at such time; provided, however,
that following a Provider Advance or a Final Advance, the Maximum Available
Commitment shall be zero.

                  "Maximum Commitment" means initially $31,820,257, as the same
may be reduced from time to time in accordance with Section 2.04(a).

                  "Non-Excluded Tax" has the meaning specified in Section 3.03.

                  "Non-Extension Advance" means an Advance made pursuant to
Section 2.02(b).

                  "Notice of Borrowing" has the meaning specified in Section
2.02(e).

                  "Notice of Replacement Subordination Agent" has the meaning
specified in Section 3.08.

                  "Participating Institution" has the meaning specified in
Section 7.08(b).


                                       5
<PAGE>   9
                                                    [REVOLVING CREDIT AGREEMENT]

                  "Participation Agreement" means, with respect to each
Indenture, the "Participation Agreement" referred to therein.

                  "Performing Equipment Note Deficiency" means any time that
less than 65% of the then aggregate outstanding principal amount of all
Equipment Notes are Performing Equipment Notes.

                  "Prospectus Supplement" means the Prospectus Supplement dated
December 7, 2000 relating to the Certificates, as such Prospectus Supplement may
be amended or supplemented.

                  "Provider Advance" means a Downgrade Advance or a
Non-Extension Advance.

                  "Regulatory Change" has the meaning specified in Section 3.01.

                  "Replenishment Amount" has the meaning assigned to such term
in Section 2.06(b).

                  "Required Amount" means, for any day, the sum of the aggregate
amount of interest, calculated at the rate per annum equal to the Stated
Interest Rate for the Class B Certificates on the basis of a 360-day year
comprised of twelve 30-day months, that would be payable on the Class B
Certificates on each of the three successive semiannual Regular Distribution
Dates following such day or, if such day is a Regular Distribution Date, on such
day and the succeeding two semiannual Regular Distribution Dates, in each case
calculated on the basis of the Pool Balance of the Class B Certificates on such
day and without regard to expected future payments of principal on the Class B
Certificates.

                  "Termination Date" means the earliest to occur of the
following: (i) the Expiry Date; (ii) the date on which the Borrower delivers to
the Liquidity Provider a certificate, signed by a Responsible Officer of the
Borrower, certifying that all of the Class B Certificates have been paid in full
(or provision has been made for such payment in accordance with the
Intercreditor Agreement and the Trust Agreement) or are otherwise no longer
entitled to the benefits of this Agreement; (iii) the date on which the Borrower
delivers to the Liquidity Provider a certificate, signed by a Responsible
Officer of the Borrower, certifying that a Replacement Liquidity Facility has
been substituted for this Agreement in full pursuant to Section 3.6(e) of the
Intercreditor Agreement; (iv) the fifth Business Day following the receipt by
the Borrower and United of a Termination Notice from the Liquidity Provider
pursuant to Section 6.01; and (v) the date on which no Advance is or may
(including by reason of reinstatement as herein provided) become available for a
Borrowing hereunder.

                  "Termination Notice" means the Notice of Termination
substantially in the form of Annex V to this Agreement.


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<PAGE>   10
                                                    [REVOLVING CREDIT AGREEMENT]

                  "Unapplied Downgrade Advance" means any Downgrade Advance
other than an Applied Downgrade Advance.

                  "Unapplied Non-Extension Advance" means any Non-Extension
Advance other than an Applied Non-Extension Advance.

                  "Unapplied Provider Advance" means any Provider Advance other
than an Applied Provider Advance.

                  "Unpaid Advance" has the meaning specified in Section 2.05.

                  "Withdrawal Notice" has the meaning specified in Section 2.10.

                  (b)      Terms Defined in the Intercreditor Agreement.  For
all purposes of this Agreement, the following terms shall have the respective
meanings assigned to such terms in the Intercreditor Agreement:

         "Acceleration," "Additional Payments," "Affiliate,"
         "Certificates,""Class A-1 Certificates," "Class A-2 Certificates,"
         "Class B Cash Collateral Account," "Class B Certificates," "Class B
         Trust ," "Class B Trust Agreement," "Class B Trustee," "Class C
         Certificates," "Closing Date," "Controlling Party," "Distribution
         Date," "Downgraded Facility," "Indenture," "Notes," "Fee Letter,"
         "Final Maturity Date," "Indentures," "Investment Earnings," "Liquidity
         Facility," "Liquidity Obligations," "Moody's," "Non-Extended
         Facility," "Note Purchase Agreement," "Operative Agreements,"
         "Aircraft", "Participation Agreements," "Performing Equipment Note,"
         "Person," "Pool Balance," "Rating Agency," "Regular Distribution Date,"
         "Replacement Liquidity Facility," "Responsible Officer," "Scheduled
         Payment," "Special Payment," "Standard & Poor's," "Stated Interest
         Rate," "Subordination Agent," "Taxes," "Threshold Rating," "Triggering
         Event," "Trust Agreement," "Trustee," "Underwriters," "Underwriting
         Agreement," "United," "United Bankruptcy Event" and "Written Notice."

                                   ARTICLE II

                       AMOUNT AND TERMS OF THE COMMITMENT

         Section 2.01      Advances. The Liquidity Provider hereby irrevocably
agrees, on the terms and conditions hereinafter set forth, to make Advances to
the Borrower from time to time on any Business Day during the period from the
Effective Date until 12:00 noon (Chicago time) on the Expiry Date (unless the
obligations of the Liquidity Provider shall be earlier terminated in accordance
with the terms of Section 2.04) in an aggregate amount at any time outstanding
not to exceed the Maximum Commitment.


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                                                    [REVOLVING CREDIT AGREEMENT]

         Section 2.02      Making the Advances. (a) Each "Interest Advance"
shall be made in a single Borrowing by delivery to the Liquidity Provider of a
written and completed Notice of Borrowing in substantially the form of Annex I,
signed by a Responsible Officer of the Borrower, such Interest Advance in an
amount not exceeding the Maximum Available Commitment at such time and shall be
used solely for the payment when due of interest on the Class B Certificates at
the Stated Interest Rate therefor in accordance with Section 3.6(a) of the
Intercreditor Agreement. Each Interest Advance made hereunder shall
automatically reduce the Maximum Available Commitment and the amount available
to be borrowed hereunder by subsequent Advances by the amount of such Interest
Advance (subject to reinstatement as provided in the next sentence). Upon
repayment to the Liquidity Provider in full or in part of the amount of any
Interest Advance made pursuant to this Section 2.02(a), together with accrued
interest thereon (as provided herein), the Maximum Available Commitment shall be
reinstated by the amount of such repaid Interest Advance, but not to exceed the
Maximum Commitment; provided, however, that the Maximum Available Commitment
shall not be so reinstated at any time if (i) a Liquidity Event of Default shall
have occurred and be continuing and (ii) there is a Performing Equipment Note
Deficiency.

                  (b)      A "Non-Extension Advance" shall be made in a single
Borrowing if this Agreement is not extended in accordance with Section 3.6(d) of
the Intercreditor Agreement (unless a Replacement Liquidity Facility to replace
this Agreement shall have been delivered to the Borrower as contemplated by said
Section 3.6(d) within the time period specified in such Section) by delivery to
the Liquidity Provider of a written and completed Notice of Borrowing in
substantially the form of Annex II attached hereto, signed by a Responsible
Officer of the Borrower, in an amount equal to the Maximum Available Commitment
at such time, and shall be used to fund the Class B Cash Collateral Account in
accordance with said Section 3.6(d) and Section 3.6(f) of the Intercreditor
Agreement.

                  (c)      A "Downgrade Advance" shall be made in a single
Borrowing upon a downgrading of the Liquidity Provider's relevant debt rating
issued by either Rating Agency below the applicable Threshold Rating (as
provided for in Section 3.6(c) of the Intercreditor Agreement) unless a
Replacement Liquidity Facility shall have been delivered to the Borrower in
accordance with said Section 3.6(c), by delivery to the Liquidity Provider of a
written and completed Notice of Borrowing in substantially the form of Annex
III, signed by a Responsible Officer of the Borrower, in an amount equal to the
Maximum Available Commitment at such time, and shall be used to fund the Class B
Cash Collateral Account in accordance with said Section 3.6(c) and Section
3.6(f). Upon such downgrading, the Liquidity Provider shall promptly deliver
notice thereof to the Borrower, the Trustee and United.

                  (d)      A "Final Advance" shall be made in a single Borrowing
upon the receipt by the Borrower of a Termination Notice from the Liquidity
Provider pursuant to Section 6.01, by delivery to the Liquidity Provider of a
written and completed Notice of Borrowing in substantially the form of Annex IV,
signed by a Responsible Officer of the Borrower, in an


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                                                    [REVOLVING CREDIT AGREEMENT]

amount equal to the Maximum Available Commitment at such time, and shall be used
to fund the Class B Cash Collateral Account (in accordance with Section 3.6(f)
and Section 3.6(i) of the Intercreditor Agreement).

                  (e)      Each Borrowing shall be made on notice in writing (a
"Notice of Borrowing") in substantially the form required by Section 2.02(a),
2.02(b), 2.02(c) or 2.02(d), as the case may be, given by the Borrower to the
Liquidity Provider. If a Notice of Borrowing is delivered by the Borrower in
respect of any Borrowing no later than 12:00 noon (Chicago time) on a Business
Day, upon satisfaction of the conditions precedent set forth in Section 4.02
with respect to a requested Borrowing, the Liquidity Provider shall, before 4:00
p.m. (Chicago time) on the date of such Borrowing or on such later Business Day
specified by the Borrower in such Notice of Borrowing, make available for the
account of its Lending Office, in U.S. dollars and in immediately available
funds, the amount of such Borrowing to be paid to the Borrower in accordance
with its payment instructions. If a Notice of Borrowing is delivered by the
Borrower in respect of any Borrowing after 12:00 noon (Chicago time) on a
Business Day, upon satisfaction of the conditions precedent set forth in Section
4.02 with respect to a requested Borrowing, the Liquidity Provider shall, before
11:00 a.m. (Chicago time) on the first Business Day following the day of receipt
of such Notice of Borrowing or on such later Business Day specified by the
Borrower in such Notice of Borrowing, make available to the Borrower, in
accordance with its payment instructions, in U.S. dollars and in immediately
available funds, the amount of such Borrowing. Payments of proceeds of a
Borrowing shall be made by wire transfer of immediately available funds to the
Borrower in accordance with such wire transfer instructions as the Borrower
shall furnish from time to time to the Liquidity Provider for such purpose. Each
Notice of Borrowing shall be irrevocable and binding on the Borrower. Each
Notice of Borrowing shall be effective upon delivery of a copy thereof to the
Liquidity Provider's New York Branch at the address specified in Section 7.02.

                  (f)      Upon the making of any Advance requested pursuant to
a Notice of Borrowing in accordance with the Borrower's payment instructions,
the Liquidity Provider shall be fully discharged of its obligation hereunder
with respect to such Notice of Borrowing, and the Liquidity Provider shall not
thereafter be obligated to make any further Advances hereunder in respect of
such Notice of Borrowing to the Borrower or to any other Person. If the
Liquidity Provider makes an Advance requested pursuant to a Notice of Borrowing
before 11:00 a.m. (Chicago time) on the second Business Day after the date of
payment specified in said Section 2.02(e), the Liquidity Provider shall have
fully discharged its obligations hereunder with respect to such Advance and an
event of default shall not have occurred hereunder. Following the making of any
Advance pursuant to Section 2.02(b), Section 2.02(c) or Section 2.02(d) to fund
the Class B Cash Collateral Account, the Liquidity Provider shall have no
interest in or rights to the Class B Cash Collateral Account, such Advance or
any other amounts from time to time on deposit in the Class B Cash Collateral
Account; provided, however, that the foregoing shall not affect or impair the
obligations of the Subordination Agent to make the distributions contemplated by
Section 3.6(e) or (f) of the Intercreditor Agreement and provided further, that


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                                                    [REVOLVING CREDIT AGREEMENT]

the foregoing shall not affect or impair the rights of the Liquidity Provider to
provide written instructions with respect to the investment and reinvestment of
the Cash Collateral Accounts to the extent provided in Section 2.2(b) of the
Intercreditor Agreement. By paying to the Borrower proceeds of Advances
requested by the Borrower in accordance with the provisions of this Agreement,
the Liquidity Provider makes no representation as to, and assumes no
responsibility for, the correctness or sufficiency for any purpose of the amount
of the Advances so made and requested.

         Section 2.03      Fees. The Borrower agrees to pay to the Liquidity
Provider the fees set forth in the Fee Letter.

         Section 2.04      Automatic Reductions and Termination of the Maximum
Commitment.

                  (a)      Automatic Reductions. Promptly following each date on
which the Required Amount is reduced as a result of a reduction in the Pool
Balance of the Class B Certificates or otherwise, the Maximum Commitment shall
automatically be reduced to an amount equal to such reduced Required Amount (as
calculated by the Borrower). The Borrower shall give notice of any such
automatic reduction of the Maximum Commitment to the Liquidity Provider within
two Business Days thereof. The failure by the Borrower to furnish any such
notice shall not affect such automatic reduction of the Maximum Commitment.

                  (b)      Termination. Upon the making of any Provider Advance
or Final Advance hereunder or the occurrence of the Termination Date, the
obligation of the Liquidity Provider to make further Advances hereunder shall
automatically and irrevocably terminate, and the Borrower shall not be entitled
to request any further Borrowing hereunder.

         Section 2.05      Repayments of Interest Advances or the Final Advance.
Subject to Sections 2.06, 2.07 and 2.09, the Borrower hereby agrees, without
notice of an Advance or demand for repayment from the Liquidity Provider (which
notice and demand are hereby waived by the Borrower), to pay, or to cause to be
paid, to the Liquidity Provider on each date on which the Liquidity Provider
shall make an Interest Advance or the Final Advance, an amount equal to (a) the
amount of such Advance (any such Advance, until repaid, is referred to herein as
an "Unpaid Advance"), plus (b) interest on the amount of each such Unpaid
Advance as provided in Section 3.07; provided, however, that if (i) the
Liquidity Provider shall make a Provider Advance at any time after making one or
more Interest Advances which shall not have been repaid in accordance with this
Section 2.05 or (ii) this Liquidity Facility shall become a Downgraded Facility
or Non-Extended Facility at any time when unreimbursed Interest Advances have
reduced the Maximum Available Commitment to zero, then such Interest Advances
shall cease to constitute Unpaid Advances and shall be deemed to have been
changed into an Applied Downgrade Advance or an Applied Non-Extension Advance,
as the case may be, for all purposes of this Agreement (including, for the
purpose of determining when such Interest Advance is required to be repaid to
the Liquidity Provider in accordance with Section 2.06 and for the


                                       10
<PAGE>   14
                                                    [REVOLVING CREDIT AGREEMENT]

purposes of Section 2.06(b)). The Borrower and the Liquidity Provider agree that
the repayment in full of each Interest Advance and Final Advance on the date
such Advance is made is intended to be a contemporaneous exchange for new value
given to the Borrower by the Liquidity Provider.

         Section 2.06      Repayments of Provider Advances.  (a)  Amounts
advanced hereunder in respect of a Provider Advance shall be deposited in the
Class B Cash Collateral Account, invested and withdrawn from the Class B Cash
Collateral Account as set forth in Sections 3.6(c), (d) and (f) of the
Intercreditor Agreement. The Borrower agrees to pay to the Liquidity Provider,
on each Regular Distribution Date, commencing on the first Regular Distribution
Date after the making of a Provider Advance, interest on the principal amount of
any such Provider Advance as provided in Section 3.07; provided, however, that
amounts in respect of a Provider Advance withdrawn from the Class B Cash
Collateral Account for the purpose of paying interest on the Class B
Certificates in accordance with Section 3.6(f) of the Intercreditor Agreement
(the amount of any such withdrawal being (y) in the case of a Downgrade Advance,
an "Applied Downgrade Advance" and (z) in the case of a Non-Extension Advance,
an "Applied Non-Extension Advance" and, together with an Applied Downgrade
Advance, an "Applied Provider Advance") shall thereafter (subject to Section
2.06(b)) be treated as an Interest Advance under this Agreement for purposes of
determining the Applicable Liquidity Rate for interest payable thereon; and
provided, further, that if, following the making of a Provider Advance, the
Liquidity Provider delivers a Termination Notice to the Borrower pursuant to
Section 6.01, such Provider Advance shall thereafter be treated as a Final
Advance under this Agreement for purposes of determining the Applicable
Liquidity Rate for interest payable thereon and the obligation for repayment
thereof. Subject to Sections 2.07 and 2.09 hereof, immediately upon the
withdrawal of any amounts from the Class B Cash Collateral Account on account of
a reduction in the Required Amount, the Borrower shall repay to the Liquidity
Provider a portion of the Provider Advances in a principal amount equal to the
amount of such reduction, plus interest on the principal amount prepaid as
provided in Section 3.07.

                  (b)      At any time when an Applied Provider Advance (or any
portion thereof) is outstanding, upon the deposit in the Class B Cash Collateral
Account of any amount pursuant to clause third of Section 2.4(b) of the
Intercreditor Agreement, clause third of Section 3.2 of the Intercreditor
Agreement or clause fourth of Section 3.3 of the Intercreditor Agreement (any
such amount being a "Replenishment Amount") for the purpose of replenishing or
increasing the balance thereof up to the amount of the Required Amount at such
time, (i) the aggregate outstanding principal amount of all Applied Provider
Advances (and of Provider Advances treated as an Interest Advance for purposes
of determining the Applicable Liquidity Rate for interest payable thereon) shall
be automatically reduced by the amount of such Replenishment Amount and (ii) the
principal amount of all outstanding Unapplied Provider Advances shall be
automatically increased by the amount of such Replenishment Amount.


                                       11
<PAGE>   15
                                                    [REVOLVING CREDIT AGREEMENT]

                  (c)      Upon the provision of a Replacement Liquidity
Facility in replacement of this Agreement in accordance with Section 3.6(e) of
the Intercreditor Agreement, amounts remaining on deposit in the Class B Cash
Collateral Account after giving effect to any Applied Provider Advance on the
date of such replacement shall be reimbursed to the Liquidity Provider, but only
to the extent such amounts are necessary to repay in full to the Liquidity
Provider all amounts owing to it hereunder.

         Section 2.07      Payments to the Liquidity Provider Under the
Intercreditor Agreement. In order to provide for payment or repayment to the
Liquidity Provider of any amounts hereunder, the Intercreditor Agreement
provides that amounts available and referred to in Articles II and III of the
Intercreditor Agreement, to the extent payable to the Liquidity Provider
pursuant to the terms of the Intercreditor Agreement (including, without
limitation, Section 3.6(f) of the Intercreditor Agreement), shall be paid to the
Liquidity Provider in accordance with the terms thereof. Amounts so paid to the
Liquidity Provider shall be applied by the Liquidity Provider to Liquidity
Obligations then due and payable in the order of priority required by the
applicable provisions of Articles II and III of the Intercreditor Agreement or,
if not provided for in the Intercreditor Agreement, then in such manner as the
Liquidity Provider shall deem appropriate.

         Section 2.08      Book Entries. The Liquidity Provider shall maintain
in accordance with its usual practice an account or accounts evidencing the
indebtedness of the Borrower resulting from Advances made from time to time and
the amounts of principal and interest payable hereunder and paid from time to
time in respect thereof; provided, however, that the failure by the Liquidity
Provider to maintain such account or accounts shall not affect the obligations
of the Borrower in respect of Advances.

         Section 2.09      Payments from Available Funds Only. All payments to
be made by the Borrower under this Agreement shall be made only from amounts
received by it that constitute Scheduled Payments or Special Payments or
payments under Section 5(b) of any Participation Agreement and Sections 4(j) and
7 of the Note Purchase Agreement, and only to the extent that the Borrower shall
have sufficient income or proceeds therefrom to enable the Borrower to make
payments in accordance with the terms hereof after giving effect to the priority
of payments provisions set forth in the Intercreditor Agreement. The Liquidity
Provider agrees that it shall look solely to such amounts to the extent
available for distribution to it as provided in the Intercreditor Agreement and
this Agreement and that the Borrower, in its individual capacity, is not
personally liable to it for any amounts payable or liability under this
Agreement except as expressly provided in this Agreement or the Intercreditor
Agreement. Amounts on deposit in the Class B Cash Collateral Account shall be
available to the Borrower to make payments under this Agreement only to the
extent and for the purposes expressly contemplated in Section 3.6(f) of the
Intercreditor Agreement.

         Section 2.10      Extension of Expiry Date. No earlier than the 60th
day and no later than the 40th day prior to the then effective Expiry Date
(unless such Expiry Date is on or after the


                                       12
<PAGE>   16
                                                    [REVOLVING CREDIT AGREEMENT]

date that is 15 days after the Final Maturity Date for the Class B
Certificates), the Borrower shall request that the Liquidity Provider extend the
Expiry Date to the earlier of (i) the date that is 15 days after the Final
Maturity Date for the Class B Certificates and (ii) the date that is the day
immediately preceding the 364th day occurring after the last day of the Consent
Period (as hereinafter defined). Whether or not the Borrower has made such
request, the Liquidity Provider shall advise the Borrower, no earlier than the
40th day (or, if earlier, the date of the Liquidity Provider's receipt of such
request, if any, from the Borrower) and no later than the 25th day prior to the
then effective Expiry Date (such period the "Consent Period"), whether, in its
sole discretion, it agrees to so extend the Expiry Date. If the Liquidity
Provider advises the Borrower on or before the date on which the Consent Period
ends that such Expiry Date shall not be so extended, or fails to irrevocably and
unconditionally advise the Borrower on or before the date on which the Consent
Period ends that such Expiry Date shall be so extended (and, in each case,
if the Liquidity Provider shall not have been replaced in accordance with
Section 3.6(e) of the Intercreditor Agreement), the Borrower shall be entitled
on and after the date on which the Consent Period ends (but prior to the then
effective Expiry Date) to request a Non-Extension Advance in accordance with
Section 2.02(b) and Section 3.6(d) of the Intercreditor Agreement.

                                   ARTICLE III

                           OBLIGATIONS OF THE BORROWER

         Section 3.01      Increased Costs. The Borrower shall pay to the
Liquidity Provider from time to time such amounts as may be necessary to
compensate the Liquidity Provider for any costs incurred by the Liquidity
Provider which are attributable to its making or maintaining any Advances
hereunder or its obligation to make any such Advances hereunder, or any
reduction in any amount receivable by the Liquidity Provider under this
Agreement or the Intercreditor Agreement in respect of any such Advances or such
obligation (such increases in costs and reductions in amounts receivable being
herein called "Additional Costs"), resulting from any change after the date of
this Agreement in U.S. federal, state, or municipal, or any foreign laws or
regulations, or the adoption or making after such date of any interpretation,
regulation, directive, guideline, requirement or request whether or not having
the force of law, by any court or governmental or monetary authority charged
with the interpretation or administration thereof (a "Regulatory Change"),
which: (1) changes the basis of taxation of any amounts payable to the Liquidity
Provider under this Agreement in respect of any such Advances or such obligation
(other than Taxes); or (2) imposes or modifies any reserve, special deposit,
compulsory loan or similar requirements relating to any extensions of credit or
other assets of, or any deposits with other liabilities of, the Liquidity
Provider (including any such Advances or such obligation or any deposits
referred to in the definition of LIBOR or related definitions). The Liquidity
Provider agrees to use reasonable efforts (consistent with its internal policy
and applicable legal and regulatory restrictions) to change the jurisdiction of
its Lending Office if making such change would avoid the need for, or reduce the
amount of, any amount payable under this Section 3.01


                                       13
<PAGE>   17
                                                    [REVOLVING CREDIT AGREEMENT]

that may thereafter accrue and would not, in the reasonable judgment of the
Liquidity Provider, be otherwise disadvantageous to the Liquidity Provider.

         The Liquidity Provider shall notify the Borrower of any event occurring
after the date of this Agreement that shall entitle the Liquidity Provider to
compensation pursuant to this Section 3.01 as promptly as practicable after it
obtains knowledge thereof and determines to request such compensation, which
notice shall describe in reasonable detail the calculation of the amounts owed
under this Section 3.01. Determinations by the Liquidity Provider for purposes
of this Section 3.01 of the effect of any Regulatory Change on its costs of
making or maintaining Advances or on amounts receivable by it in respect of
Advances, and of the additional amounts required to compensate the Liquidity
Provider in respect of any Additional Costs, shall be prima facie evidence of
the amount owed under this Section 3.01.

         Notwithstanding the preceding two paragraphs, the Liquidity Provider
and the Subordination Agent agree that any permitted assignee or participant of
the initial Liquidity Provider that is not a bank shall not be entitled to the
benefits of the preceding two paragraphs (but without limiting the provisions of
Section 7.08 hereof).

         Section 3.02      Capital Adequacy. If (1) compliance with any
judicial, administrative or other governmental interpretation of any law or
regulation or (2) compliance by the Liquidity Provider or any corporation
controlling the Liquidity Provider with any guideline or request from any
central bank or other governmental authority (whether or not having the force of
law) has the effect of requiring an increase in the amount of capital required
or expected to be maintained by the Liquidity Provider or any corporation
controlling the Liquidity Provider, and such increase is based upon the
Liquidity Provider's obligations hereunder and other similar obligations, the
Borrower shall pay to the Liquidity Provider such additional amount as shall be
reasonably allocable to the Liquidity Provider's obligations to the Borrower
hereunder. The Liquidity Provider agrees to use reasonable efforts (consistent
with applicable legal and regulatory restrictions) to change the jurisdiction of
its Lending Office if making such change would avoid the need for, or reduce the
amount of, any amount payable under this Section 3.02 that may thereafter accrue
and would not, in the reasonable judgment of the Liquidity Provider, be
otherwise disadvantageous to the Liquidity Provider.

         The Liquidity Provider shall notify the Borrower of any event occurring
after the date of this Agreement that shall entitle the Liquidity Provider to
compensation pursuant to this Section 3.02 as promptly as practicable after it
obtains knowledge thereof and determines to request such compensation, which
notice shall describe in reasonable detail the calculation of the amounts owed
under this Section 3.02. Determinations by the Liquidity Provider for purposes
of this Section 3.02 of the effect of any increase in the amount of capital
required to be maintained by the Liquidity Provider and of the amount allocable
to the Liquidity Provider's obligations to the Borrower hereunder shall be prima
facie evidence of the amounts owed under this Section 3.02.


                                       14
<PAGE>   18
                                                    [REVOLVING CREDIT AGREEMENT]

         Notwithstanding the preceding two paragraphs, the Liquidity Provider
and the Subordination Agent agree that any permitted assignee or participant of
the initial Liquidity Provider that is not a bank shall not be entitled to the
benefits of the preceding two paragraphs (but without limiting the provisions of
Section 7.08 hereof).

         Section 3.03      Payments Free of Deductions. (a) All payments made by
the Borrower under this Agreement shall be made free and clear of, and without
reduction for or on account of, any Taxes, excluding Excluded Taxes (such
non-excluded taxes being referred to herein, collectively, as "Non-Excluded
Taxes"). If any Non-Excluded Taxes are required to be withheld or deducted from
any amounts payable to the Liquidity Provider under this Agreement, the Borrower
shall (i) within the time prescribed therefor by applicable law pay to the
appropriate governmental or taxing authority the full amount of any such
Non-Excluded Taxes (and any additional Non-Excluded Taxes in respect of the
payment required under clause (ii) below) and make such reports or returns in
connection therewith at the time or times and in the manner prescribed by
applicable law, and (ii) pay to the Liquidity Provider an additional amount
which (after deduction of all such Non-Excluded Taxes) shall be sufficient to
yield to the Liquidity Provider the full amount which would have been received
by it had no such withholding or deduction been made. Within 30 days after the
date of each payment hereunder, the Borrower shall furnish to the Liquidity
Provider the original or a certified copy of (or other documentary evidence of)
the payment of the Non-Excluded Taxes applicable to such payment. The Liquidity
Provider agrees to use reasonable efforts (consistent with applicable legal and
regulatory restrictions) to change the jurisdiction of its Lending Office if
making such change would avoid the need for, or reduce the amount of, any such
additional amounts that may thereafter accrue and would not, in the reasonable
judgment of the Liquidity Provider, be otherwise materially disadvantageous (as
determined by the Liquidity Provider) to the Liquidity Provider or require the
Liquidity Provider to incur any cost or expenses for which it is not indemnified
by the Borrower. The Liquidity Provider shall deliver to the Borrower such
certificates and documents as may be reasonably requested by the Borrower and
required by applicable law and as may be legally delivered by the Liquidity
Provider to establish that payments hereunder are exempt from (or entitled to a
reduced rate of) withholding Tax.

                  (b)      All payments (including, without limitation,
Advances) made by the Liquidity Provider under this Agreement shall be made free
and clear of, and without reduction for or on account of, any Taxes. If any
Taxes are required to be withheld or deducted from any amounts payable to the
Borrower under this Agreement, the Liquidity Provider shall (i) within the time
prescribed therefor by applicable law pay to the appropriate governmental or
taxing authority the full amount of any such Taxes (and any additional Taxes in
respect of the additional amounts payable under clause (ii) hereof) and make
such reports or returns in connection therewith at the time or times and in the
manner prescribed by applicable law, and (ii) pay to the Borrower an additional
amount which (after deduction of all such Taxes) shall be sufficient to yield to
the Borrower the full amount which would have been received by it had no such
withholding or deduction been made. Within 30 days after the date of each
payment hereunder,


                                       15
<PAGE>   19
                                                    [REVOLVING CREDIT AGREEMENT]

the Liquidity Provider shall furnish to the Borrower the original or a certified
copy of (or other documentary evidence of) the payment of the Taxes applicable
to such payment.

                  (c)      If any exemption from, or reduction in the rate of,
any Taxes is reasonably available to the Borrower to establish that payments
under this Agreement are exempt from (or entitled to a reduced rate of) tax, the
Borrower shall deliver to the Liquidity Provider such form or forms and such
other evidence of the eligibility of the Borrower for such exemption or
reduction as the Liquidity Provider may reasonably identify to the Borrower as
being required as a condition to exemption from, or reduction in the rate of,
any Taxes.

         Section 3.04      Payments. The Borrower shall make or cause to be made
each payment to the Liquidity Provider under this Agreement so as to cause the
same to be received by the Liquidity Provider not later than 1:00 P.M. (Chicago
time) on the day when due. The Borrower shall make all such payments in lawful
money of the United States of America, to the Liquidity Provider in immediately
available funds, by wire transfer to The Chase Manhattan Bank, New York, ABA No.
021000021, Account Name: Westdeutsche Landesbank Girozentrale, New York Branch,
Account No. 920-1-060663, ref: United Airlines 2000-2B.

         Section 3.05      Computations. All computations of interest based on
the Base Rate shall be made on the basis of a year of 365 or 366 days, as the
case may be, and all computations of interest based on the LIBOR shall be made
on the basis of a year of 360 days, in each case for the actual number of days
(including the first day but excluding the last day) occurring in the period for
which such interest is payable.

         Section 3.06      Payment on Non-Business Days. Whenever any payment to
be made hereunder shall be stated to be due on a day other than a Business Day,
such payment shall be made on the next Business Day and no additional interest
shall be due as a result (and if so made, shall be deemed to have been made when
due). If any payment in respect of interest on an Advance is so deferred to the
next Business Day, such deferral shall not delay the commencement of the next
Interest Period for such Advance (if such Advance is a LIBOR Advance) or reduce
the number of days for which interest shall be payable on such Advance on the
next interest payment date for such Advance.

         Section 3.07      Interest. (a) Subject to Section 2.09, the Borrower
shall pay, or shall cause to be paid, without duplication, interest on (i) the
unpaid principal amount of each Advance from and including the date of such
Advance (or, in the case of an Applied Provider Advance, from and including the
date on which the amount thereof was withdrawn from the Class B Cash Collateral
Account to pay interest on the Class B Certificates) to but excluding the date
such principal amount shall be paid in full (or, in the case of an Applied
Provider Advance, the date on which the Class B Cash Collateral Account is fully
replenished in respect of such Advance) and (ii) any other amount due hereunder
(whether fees, commissions, expenses or other amounts or to the extent permitted
by applicable law, installments of interest on Advances or any such other


                                       16
<PAGE>   20
                                                    [REVOLVING CREDIT AGREEMENT]

amount) which is not paid when due (whether at stated maturity, by acceleration
or otherwise) from and including the due date thereof to but excluding the date
such amount is paid in full, in each such case, at a fluctuating interest rate
per annum for each day equal to the Applicable Liquidity Rate (as defined below)
for such Advance or such other amount as in effect for such day, but in no event
at a rate per annum greater than the maximum rate permitted by applicable law;
provided, however, that, if at any time the otherwise applicable interest rate
as set forth in this Section 3.07 shall exceed the maximum rate permitted by
applicable law, then any subsequent reduction in such interest rate shall not
reduce the rate of interest payable pursuant to this Section 3.07 below the
maximum rate permitted by applicable law until the total amount of interest
accrued equals the amount of interest that would have accrued if such otherwise
applicable interest rate as set forth in this Section 3.07 had at all times been
in effect. Nothing contained in this Section 3.07 shall require the Borrower to
pay any amount under this Section 3.07 other than to the extent the Borrower
shall have funds available therefor.

                  (b)      Except as provided in Section 3.07(e), each Advance
shall be either a Base Rate Advance or a LIBOR Advance as provided in this
Section or Section 3.10. Each such Advance shall be a Base Rate Advance for the
period from the date of its borrowing to (but excluding) the third Business Day
following the Liquidity Provider's receipt of the Notice of Borrowing for such
Advance. Thereafter, such Advance shall be a LIBOR Advance; provided, however,
that the Borrower (at the direction of the Controlling Party, so long as the
Liquidity Provider is not the Controlling Party) may (x) convert the Final
Advance into a Base Rate Advance on the last day of an Interest Period for such
Advance by giving the Liquidity Provider no less than four Business Days' prior
written notice of such election or (y) elect to maintain the Final Advance as a
Base Rate Advance by not requesting a conversion of the Final Advance to a LIBOR
Advance under Clause (5) of the applicable Notice of Borrowing (or, if such
Final Advance is deemed to have been made, without delivery of a Notice of
Borrowing pursuant to Section 2.06, by requesting, prior to 11:00 A.M. (New York
time) on the first Business Day following the Borrower's receipt of the
applicable Termination Notice, that such Final Advance not be converted from a
Base Rate Advance to a LIBOR Advance).

                  (c)      Each LIBOR Advance shall bear interest during each
Interest Period at a rate per annum equal to LIBOR for such Interest Period plus
the Applicable Margin for such LIBOR Advance, payable in arrears on the last day
of such Interest Period and, in the event of the payment of principal of such
LIBOR Advance on a day other than such last day, on the date of such payment (to
the extent of interest accrued on the amount of principal repaid).

                  (d)      Each Base Rate Advance shall bear interest at a rate
per annum equal to the Base Rate plus the Applicable Margin for such Base Rate
Advance, payable in arrears on each Regular Distribution Date and, in the event
of the payment of principal of such Base Rate Advance on a day other than a
Regular Distribution Date, on the date of such payment (to the extent of
interest accrued on the amount of principal repaid).


                                       17
<PAGE>   21
                                                    [REVOLVING CREDIT AGREEMENT]

                  (e)      Each Unapplied Provider Advance shall bear interest
in an amount equal to the Investment Earnings on amounts on deposit in the Class
B Cash Collateral Account, payable in arrears on each Regular Distribution Date.

                  (f)      Each amount not paid when due hereunder (whether
fees, commissions, expenses or other amounts or, to the extent permitted by
applicable law, installments of interest on Advances but excluding Advances)
shall bear interest at a rate per annum equal to the Base Rate plus 2.00% per
annum.

                  (g)      Each change in the Base Rate shall become effective
immediately. The rates of interest specified in this Section 3.07 with respect
to any Advance or other amount shall be referred to as the "Applicable Liquidity
Rate."

         Section 3.08      Replacement of Borrower.  Subject to Section 5.02,
from time to time and subject to the successor Borrower's meeting the
eligibility requirements set forth in Section 6.9 of the Intercreditor Agreement
applicable to the Subordination Agent, upon the effective date and time
specified in a written and completed Notice of Replacement Subordination Agent
in substantially the form of Annex VI (a "Notice of Replacement Subordination
Agent") delivered to the Liquidity Provider by the then Borrower, the successor
Borrower designated therein shall be substituted for as the Borrower for all
purposes hereunder.

         Section 3.09      Funding Loss Indemnification. The Borrower shall pay
to the Liquidity Provider, upon the request of the Liquidity Provider, such
amount or amounts as shall be sufficient (in the reasonable opinion of the
Liquidity Provider) to compensate it for any loss, cost, or expense incurred by
reason of the liquidation or redeployment of deposits or other funds acquired by
the Liquidity Provider to fund or maintain any LIBOR Advance (but excluding loss
of anticipated profits) incurred as a result of:

                  (1)      Any repayment of a LIBOR Advance on a date other than
         the last day of the Interest Period for such Advance; or

                  (2)      Any failure by the Borrower to borrow a LIBOR Advance
         on the date for borrowing specified in the relevant notice under
         Section 2.02.

         Section 3.10      Illegality. Notwithstanding any other provision in
this Agreement, if any change in any applicable law, rule or regulation, or any
change in the interpretation or administration thereof by any governmental
authority, central bank or comparable agency charged with the interpretation or
administration thereof, or compliance by the Liquidity Provider (or its Lending
Office) with any request or directive (whether or not having the force of law)
of any such authority, central bank or comparable agency shall make it unlawful
or impossible for the Liquidity Provider (or its Lending Office) to maintain or
fund its LIBOR Advances, then upon notice to the Borrower by the Liquidity
Provider, the outstanding principal amount of the


                                       18
<PAGE>   22
                                                    [REVOLVING CREDIT AGREEMENT]

LIBOR Advances shall be converted to Base Rate Advances (a) immediately upon
demand of the Liquidity Provider, if such change or compliance with such
request, in the judgment of the Liquidity Provider, requires immediate
repayment; or (b) at the expiration of the last Interest Period to expire before
the effective date of any such change or request.

                                   ARTICLE IV

                              CONDITIONS PRECEDENT

         Section 4.01      Conditions Precedent to Effectiveness of Section
2.01. Section 2.01 of this Agreement shall become effective on and as of the
first date (the "Effective Date") on which the following conditions precedent
have been satisfied or waived:

                  (a)      The Liquidity Provider shall have received on or
before the Closing Date each of the following, each dated such date, and in the
case of each document delivered pursuant to paragraphs (i), (ii) and (iii), in
form and substance satisfactory to the Liquidity Provider:

                           (i)      This Agreement duly executed on behalf of
         the Borrower;

                           (ii)     The Intercreditor Agreement duly executed on
         behalf of each of the parties thereto (other than the Liquidity
         Provider);

                           (iii)    Fully executed copies of each of the
         Operative Agreements (other than this Agreement and the Intercreditor
         Agreement);

                           (iv)     A copy of the Prospectus Supplement and
         specimen copies of the Class B Certificates;

                           (v)      An executed copy of each opinion, document,
         instrument and certificate delivered pursuant to the Class B Trust
         Agreement, the Intercreditor Agreement, the Note Purchase Agreement and
         the other Operative Agreements (together with, in the case of each such
         opinion, other than the opinion of counsel for the Underwriters, either
         addressed to the Liquidity Provider or accompanied by a letter from the
         counsel rendering such opinion to the effect that the Liquidity
         Provider is entitled to rely on such opinion as of its date as if it
         were addressed to the Liquidity Provider);

                           (vi)     Evidence that there shall have been made and
         shall be in full force and effect, all filings, recordings and/or
         registrations, and there shall have been given or taken any notice or
         other similar action as may be reasonably necessary or, to the extent
         reasonably requested by the Liquidity Provider, reasonably advisable,
         in order to establish, perfect, protect and preserve the right, title
         and interest, remedies, powers,


                                       19
<PAGE>   23
                                                    [REVOLVING CREDIT AGREEMENT]

         privileges, liens and security interests of, or for the benefit of, the
         Trustee and the Liquidity Provider created by the Operative Agreements;
         and

                           (vii)    Such other documents, instruments, opinions
         and approvals as the Liquidity Provider shall have reasonably
         requested.

                  (b)      The following statements shall be true on and as of
the Effective Date:

                           (i)      The representations and warranties in the
         Note Purchase Agreement and each of the Participation Agreements are
         true and correct on and as of the Effective Date as though made on and
         as of the Effective Date;

                           (ii)     No event has occurred and is continuing, or
         would result from the entering into of this Agreement or the making of
         any Advance, which constitutes a Liquidity Event of Default; and

                           (iii)    There has been no material adverse change in
         the financial condition or results of operations of United and its
         subsidiaries taken as a whole since September 30, 2000.

                  (c)      The Liquidity Provider shall have received payment in
full of all fees and other sums required to be paid to or for the account of the
Liquidity Provider on or prior to the Effective Date.

                  (d)      All conditions precedent to the issuance of the
Certificates under the Trust Agreements shall have been satisfied or waived, all
conditions precedent to the effectiveness of the other Liquidity Facilities
shall have been satisfied or waived, and all conditions precedent to the
purchase of the Certificates by the Underwriters under the Underwriting
Agreement shall have been satisfied (unless any of such conditions precedent
shall have been waived by the Underwriters).

                  (e)      The Borrower shall have received a certificate, dated
the date hereof, signed by a duly authorized representative of the Liquidity
Provider, certifying that all conditions precedent to the effectiveness of
Section 2.01 have been satisfied or waived.

         Section 4.02      Conditions Precedent to Borrowing. The obligation of
the Liquidity Provider to make an Advance on the occasion of each Borrowing
shall be subject to the conditions precedent that the Effective Date shall have
occurred and, prior to the date of such Borrowing, the Borrower shall have
delivered a Notice of Borrowing which conforms to the terms and conditions of
this Agreement and has been completed as may be required by the relevant form of
the Notice of Borrowing for the type of Advances requested.


                                       20
<PAGE>   24

                                                    [REVOLVING CREDIT AGREEMENT]

                                    ARTICLE V

                                    COVENANTS

         Section 5.01      Affirmative Covenants of the Borrower. So long as any
Advance shall remain unpaid or the Liquidity Provider shall have any Maximum
Commitment hereunder or the Borrower shall have any obligation to pay any amount
to the Liquidity Provider hereunder, the Borrower shall, unless the Liquidity
Provider shall otherwise consent in writing:

                  (a)      Performance of Agreements. Punctually pay or cause to
be paid all amounts payable by it under this Agreement and the other Operative
Agreements and observe and perform in all material respects the conditions,
covenants and requirements applicable to it contained in this Agreement and the
other Operative Agreements.

                  (b)      Reporting Requirements. Furnish to the Liquidity
Provider with reasonable promptness, such other information and data with
respect to the transactions contemplated by the Operative Agreements as from
time to time may be reasonably requested by the Liquidity Provider; and permit
the Liquidity Provider, upon reasonable notice, to inspect the Borrower's books
and records with respect to such transactions and to meet with officers and
employees of the Borrower to discuss such transactions.

                  (c)      Certain Operative Agreements.  Furnish to the
Liquidity Provider with reasonable promptness any Operative Agreement entered
into after the date hereof.

         Section 5.02      Negative Covenants of the Borrower. So long as any
Advance shall remain unpaid or the Liquidity Provider shall have any Maximum
Commitment hereunder or the Borrower shall have any obligation to pay any amount
to the Liquidity Provider hereunder, the Borrower shall not appoint or permit or
suffer to be appointed any successor Borrower without the written consent of the
Liquidity Provider, which consent shall not be unreasonably withheld or delayed.


                                   ARTICLE VI

                           LIQUIDITY EVENTS OF DEFAULT

         Section 6.01      Liquidity Events of Default. If (a) any Liquidity
Event of Default has occurred and is continuing and (b) there is a Performing
Equipment Note Deficiency, the Liquidity Provider may, in its discretion,
deliver to the Borrower a Termination Notice, the effect of which shall be to
cause (i) the obligation of the Liquidity Provider to make Advances hereunder to
expire on the fifth Business Day after the date on which such Termination Notice
is received by the Borrower, (ii) the Borrower to promptly request, and the
Liquidity Provider to promptly make, a Final Advance in accordance with Section
2.02(d) and Section 3.6(i) of the Intercreditor Agreement, (iii) all other
outstanding Advances to be automatically converted into


                                       21
<PAGE>   25
                                                    [REVOLVING CREDIT AGREEMENT]

Final Advances for purposes of determining the Applicable Liquidity Rate for
interest payable thereon, and (iv) subject to Sections 2.07 and 2.09, all
Advances (including, without limitation, any Provider Advance and Applied
Provider Advance), any accrued interest thereon and any other amounts
outstanding hereunder to become immediately due and payable to the Liquidity
Provider.

                                   ARTICLE VII

                                  MISCELLANEOUS

         Section 7.01      Amendments, Etc. No amendment or waiver of any
provision of this Agreement, nor consent to any departure by the Borrower
therefrom, shall in any event be effective unless the same shall be in writing
and signed by the Liquidity Provider, and, in the case of an amendment, the
Borrower, and then such waiver or consent shall be effective only in the
specific instance and for the specific purpose for which given.

         Section 7.02      Notices, Etc. Except as otherwise expressly provided
herein, all notices and other communications provided for hereunder shall be in
writing (including sent by telecopier):

     Borrower:          State Street Bank and Trust Company of Connecticut,
                        National Association
                        225 Asylum Street
                        Goodwin Square
                        Hartford, Connecticut 06103
                        Attention: Corporate Trust Division

                        Telephone: 860-244-1844
                        Telecopy:  860-244-1881

     Liquidity
     Provider:          Westdeutsche Landesbank Girozentrale
                        New York Branch
                        1211 Avenue of the Americas
                        New York, New York  10036
                        Business/Credit Contact
                        Attention:  Transportation Finance
                        Global Structured Finance/Americas

                        Telephone: 212-852-6115
                        Telecopy:  212-869-7634


                                       22
<PAGE>   26
                                                    [REVOLVING CREDIT AGREEMENT]

                        Operations Contact
                        Attention: Philip Green
                                   Loan Administration

                        Telephone:  212-852-6113
                        Telecopy:   212-302-7946

or, as to each of the foregoing, at such other address as shall be designated by
such Person in a Written Notice to the others. All such notices and
communications shall be effective (i) if given by telecopier, when transmitted
to the telecopier number specified above with receipt confirmed, (ii) if given
by mail, when deposited in the mails addressed as specified above, and (iii) if
given by other means, when delivered at the address specified above, except that
Written Notices to the Liquidity Provider pursuant to the provisions of Articles
II and III shall not be effective until received by the Liquidity Provider,
subject to the last sentence of Section 2.02(e). A copy of all notices delivered
hereunder to either party shall in addition be delivered to each of the parties
to the Participation Agreements at their respective addresses set forth therein.

         Section 7.03      No Waiver; Remedies. No failure on the part of the
Liquidity Provider to exercise, and no delay in exercising, any right under this
Agreement shall operate as a waiver thereof; nor shall any single or partial
exercise of any right under this Agreement preclude any other or further
exercise thereof or the exercise of any other right. The remedies herein
provided are cumulative and not exclusive of any remedies provided by law.

         Section 7.04      Further Assurances. The Borrower agrees to do such
further acts and things and to execute and deliver to the Liquidity Provider
such additional assignments, agreements, powers and instruments as the Liquidity
Provider may reasonably require or deem advisable to carry into effect the
purposes of this Agreement and the other Operative Agreements or to better
assure and confirm unto the Liquidity Provider its rights, powers and remedies
hereunder and under the other Operative Agreements.

         Section 7.05      Indemnification; Survival of Certain Provisions. The
Liquidity Provider shall be indemnified hereunder to the extent and in the
manner described in Section 5(b) of any Participation Agreement. In addition,
the Borrower agrees to indemnify, protect, defend and hold harmless the
Liquidity Provider from, against and in respect of, and shall pay on demand, all
Expenses (including the expenses set forth in Section 7 of the Note Purchase
Agreement) of any kind or nature whatsoever (other than any Expenses of the
nature described in Section 3.01, 3.02 or 7.07 hereof or in the Fee Letter
(regardless of whether indemnified against pursuant to said Sections or in such
Fee Letter)) that may be imposed, incurred by or asserted against any Liquidity
Indemnitee, in any way relating to, resulting from, or arising out of or in
connection with any action, suit or proceeding by any third party against such
Liquidity Indemnitee and relating to this Agreement, the Intercreditor
Agreement, the Fee Letter or any Participation Agreement; provided, however,
that the Borrower shall not be required to indemnify, protect,


                                       23
<PAGE>   27
                                                    [REVOLVING CREDIT AGREEMENT]

defend and hold harmless any Liquidity Indemnitee in respect of any Expense of
such Liquidity Indemnitee to the extent such Expense is (i) attributable to the
gross negligence or willful misconduct of such Liquidity Indemnitee or any other
Liquidity Indemnitee, (ii) ordinary and usual operating overhead expense or
(iii) attributable to the failure by such Liquidity Indemnitee or any other
Liquidity Indemnitee to perform or observe any agreement, covenant or condition
on its part to be performed or observed in this Agreement, the Intercreditor
Agreement, the Fee Letter or any other Operative Agreement to which it is a
party. The indemnities and cost provisions contained in Section 4(j) of the Note
Purchase Agreement and Section 5(b) of any Participation Agreement and the
provisions of Sections 3.01, 3.02, 3.03, 3.09 7.05 and 7.07 shall survive the
termination of this Agreement.

         Section 7.06      Liability of the Liquidity Provider. (a) Neither the
Liquidity Provider nor any of its officers, directors, employees or affiliates
shall be liable or responsible for: (i) the use which may be made of the
Advances or any acts or omissions of the Borrower or any beneficiary or
transferee in connection therewith; (ii) the validity, sufficiency or
genuineness of documents, or of any endorsement thereon, even if such documents
should prove to be in any or all respects invalid, insufficient, fraudulent or
forged; or (iii) the making of Advances by the Liquidity Provider against
delivery of a Notice of Borrowing and other documents which do not comply
with the terms hereof; provided, however, that the Borrower shall have a claim
against the Liquidity Provider, and the Liquidity Provider shall be liable to
the Borrower, to the extent of any damages suffered by the Borrower which were
the result of (A) the Liquidity Provider's willful misconduct or negligence in
determining whether documents presented hereunder comply with the terms hereof,
or (B) any breach by the Liquidity Provider of any of the terms of this
Agreement, including, but not limited to, the Liquidity Provider's failure to
make lawful payment hereunder after the delivery to it by the Borrower of a
Notice of Borrowing complying with the terms and conditions hereof.

                  (b)      Neither the Liquidity Provider nor any of its
officers, employees, directors or Affiliates shall be liable or responsible in
any respect for (i) any error, omission, interruption or delay in transmission,
dispatch or delivery of any message or advice, however transmitted, in
connection with this Agreement or any Notice of Borrowing delivered hereunder,
or (ii) any action, inaction or omission which may be taken by it in good faith,
absent willful misconduct or negligence (in which event the extent of the
Liquidity Provider's potential liability to the Borrower shall be limited as set
forth in the preceding paragraph), in connection with this Agreement or any
Notice of Borrowing.

         Section 7.07      Costs, Expenses and Taxes. The Borrower agrees to
pay, or cause to be paid (A) on the Effective Date and on such later date or
dates on which the Liquidity Provider shall make demand, all reasonable
out-of-pocket costs and expenses of the Liquidity Provider in connection with
the preparation, negotiation, execution, delivery, filing and recording of this
Agreement, any other Operative Agreement and any other documents which may be
delivered in connection with this Agreement, including, without limitation, the
reasonable fees and expenses


                                       24
<PAGE>   28
                                                    [REVOLVING CREDIT AGREEMENT]

of outside counsel for the Liquidity Provider and (B) on demand, all reasonable
costs and expenses of the Liquidity Provider (including reasonable counsel fees
and expenses) in connection with (i) the enforcement of this Agreement or any
other Operative Agreement, (ii) the modification or amendment of, or supplement
to, this Agreement or any other Operative Agreement or such other documents
which may be delivered in connection herewith or therewith (whether or not the
same shall become effective) or (iii) any action or proceeding relating to any
order, injunction, or other process or decree restraining or seeking to restrain
the Liquidity Provider from paying any amount under this Agreement, the
Intercreditor Agreement or any other Operative Agreement or otherwise affecting
the application of funds in the Class B Cash Collateral Account. In addition,
the Borrower shall pay any and all recording, stamp and other similar taxes and
fees payable or determined to be payable in connection with the execution,
delivery, filing and recording of this Agreement any other Operative Agreement
and such other documents, and agrees to save the Liquidity Provider harmless
from and against any and all liabilities with respect to or resulting from any
delay in paying or omission to pay such taxes or fees.

         Section 7.08      Binding Effect; Participations. (a) This Agreement
shall be binding upon and inure to the benefit of the Borrower and the Liquidity
Provider and their respective successors and assigns, except that neither the
Liquidity Provider (except as otherwise provided in this Section 7.08) nor the
Borrower (except as contemplated by Section 3.08) shall have the right to assign
its rights or obligations hereunder or any interest herein without the prior
written consent of the other party, subject to the requirements of Section
7.08(b). The Liquidity Provider may grant participations herein or in any of its
rights hereunder and under the other Operative Agreements to such Persons (other
than United or any of its Affiliates) as the Liquidity Provider may in its sole
discretion select, subject to the requirements of Section 7.08(b). No such
participation by the Liquidity Provider, however, shall relieve the Liquidity
Provider of its obligations hereunder. In connection with any participation or
any proposed participation, the Liquidity Provider may disclose to the
participant or the proposed participant any information that the Borrower is
required to deliver or to disclose to the Liquidity Provider pursuant to this
Agreement. The Borrower acknowledges and agrees that the Liquidity Provider's
source of funds may derive in part from its participants. Accordingly,
references in this Agreement and the other Operative Agreements to
determinations, reserve and capital adequacy requirements, increased costs,
reduced receipts and the like as they pertain to the Liquidity Provider shall be
deemed also to include those of each of its participants that are banks
(subject, in each case, to the maximum amount that would have been incurred by
or attributable to the Liquidity Provider directly if the Liquidity Provider,
rather than the participant, had held the interest participated other than a
result of a change in law following the date of any participation).

                  (b)      If, pursuant to Section 7.08(a) above, the Liquidity
Provider sells any participation in this Agreement to any bank or other entity
(each, a "Participating Institution"), then, concurrently with the effectiveness
of such participation, the Participating Institution shall (i) represent to the
Liquidity Provider (for the benefit of the Liquidity Provider and the Borrower)



                                       25
<PAGE>   29
                                                    [REVOLVING CREDIT AGREEMENT]

either (A) that it is incorporated under the laws of the United States or a
state thereof or (B) that under applicable law and treaties, no taxes shall be
required to be withheld by the Borrower or the Liquidity Provider with respect
to any payments to be made to such Participating Institution in respect of this
Agreement, (ii) furnish to the Liquidity Provider and the Borrower either (x) a
statement that it is incorporated under the laws of the United States or a state
thereof or (y) if it is not so incorporated, two copies of a properly completed
United States Internal Revenue Service Form W-8ECI or Form W-8BEN, as
appropriate, or other applicable form, certificate or document prescribed by the
Internal Revenue Service certifying, in each case, such Participating
Institution's entitlement to a complete exemption from United States federal
withholding tax in respect to any and all payments to be made hereunder, and
(iii) agree (for the benefit of the Liquidity Provider and the Borrower) to
provide the Liquidity Provider and the Borrower a new Form W-8ECI or Form
W-8BEN, as appropriate, (A) on or before the date that any such form expires or
becomes obsolete or (B) after the occurrence of any event requiring a change in
the most recent form previously delivered by it and prior to the immediately
following due date of any payment by the Borrower hereunder, certifying in the
case of a Form W-8BEN or Form W-8ECI that such Participating Institution is
entitled to a complete exemption from United States federal withholding tax on
payments under this Agreement. Unless the Borrower has received forms or other
documents reasonably satisfactory to it (and required by applicable law) from
the Participating Institution indicating that payments hereunder are not subject
to United States federal withholding tax, the Borrower shall withhold taxes as
required by law from such payments at the applicable statutory rate without any
obligation to make additional payments under Section 3.03.

                  (c)      Notwithstanding the other provisions of this Section
7.08, the Liquidity Provider may assign and pledge all or any portion of the
Advances owing to it to any Federal Reserve Bank or the United States Treasury
as collateral security pursuant to Regulation A of the Board of Governors of the
Federal Reserve System and any Operating Circular issued by such Federal Reserve
Bank, provided that any payment in respect of such assigned Advances made by the
Borrower to the Liquidity Provider in accordance with the terms of this
Agreement shall satisfy the Borrower's obligations hereunder in respect of such
assigned Advance to the extent of such payment. No such assignment shall release
the Liquidity Provider from its obligations hereunder.

         Section 7.09      Severability. Any provision of this Agreement which
is prohibited, unenforceable or not authorized in any jurisdiction shall, as to
such jurisdiction, be ineffective to the extent of such prohibition,
unenforceability or non-authorization without invalidating the remaining
provisions hereof or affecting the validity, enforceability or legality of such
provision in any other jurisdiction.

         Section 7.10      GOVERNING LAW. THIS AGREEMENT 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 LAWS THEREOF


                                       26
<PAGE>   30
                                                    [REVOLVING CREDIT AGREEMENT]

(OTHER THAN SECTION 5-1401 OF THE NEW YORK GENERAL OBLIGATIONS LAW)) AND THE
OBLIGATIONS, RIGHTS AND REMEDIES OF THE PARTIES UNDER THIS AGREEMENT SHALL BE
DETERMINED IN ACCORDANCE WITH SUCH LAWS.

         Section 7.11      Submission to Jurisdiction; Waiver of Jury Trial;
Waiver of Immunity.

                  (a)      Each of the parties hereto hereby irrevocably and
         unconditionally:

                           (i)      submits for itself and its property in any
         legal action or proceeding relating to this Agreement or any other
         Operative Agreement, or for recognition and enforcement of any judgment
         in respect hereof or thereof, to the non-exclusive general jurisdiction
         of the courts of the State of New York, the courts of the United States
         of America for the Southern District of New York, and the appellate
         courts from any thereof;

                           (ii)     consents that any such action or proceeding
         may be brought in such courts, and waives any objection that it may now
         or hereafter have to the venue of any such action or proceeding in any
         such court or that such action or proceeding was brought in an
         inconvenient court and agrees not to plead or claim the same;

                           (iii)    agrees that service of process in any such
         action or proceeding may be effected by mailing a copy thereof by
         registered or certified mail (or any substantially similar form of
         mail), postage prepaid, to each party hereto at its address set forth
         in Section 7.02, or at such other address of which the Liquidity
         Provider shall have been notified pursuant thereto; and

                           (iv)     agrees that nothing herein shall affect the
         right to effect service of process in any other manner permitted by law
         or shall limit the right to sue in any other jurisdiction.

                  (b)      THE BORROWER AND THE LIQUIDITY PROVIDER EACH HEREBY
AGREE TO WAIVE THEIR RESPECTIVE RIGHTS TO A JURY TRIAL OF ANY CLAIM OR CAUSE OF
ACTION BASED UPON OR ARISING OUT OF THIS AGREEMENT OR ANY DEALINGS BETWEEN THEM
RELATING TO THE SUBJECT MATTER OF THIS AGREEMENT AND THE RELATIONSHIP THAT IS
BEING ESTABLISHED, including, without limitation, contract claims, tort claims,
breach of duty claims and all other common law and statutory claims. The
Borrower and the Liquidity Provider each warrant and represent that it has
reviewed this waiver with its legal counsel, and that it knowingly and
voluntarily waives its jury trial rights following consultation with such legal
counsel. THIS WAIVER IS IRREVOCABLE, AND CANNOT BE MODIFIED EITHER ORALLY OR IN
WRITING, AND THIS WAIVER SHALL APPLY TO ANY SUBSEQUENT AMENDMENTS, RENEWALS,
SUPPLEMENTS OR MODIFICATIONS TO THIS AGREEMENT.


                                       27
<PAGE>   31
                                                    [REVOLVING CREDIT AGREEMENT]

                  (c)      The Liquidity Provider hereby waives any immunity it
may have from the jurisdiction of the courts of the United States or of any
State and waives any immunity any of its properties located in the United States
may have from attachment or execution upon a judgment entered by any such court
under the United States Foreign Sovereign Immunities Act of 1976 or any similar
successor legislation.

         Section 7.12      Execution in Counterparts. This Agreement may be
executed in any number of counterparts and by different parties hereto on
separate counterparts, each of which counterpart, when so executed and
delivered, shall be deemed to be an original and all of which counterparts,
taken together, shall constitute but one and the same Agreement.

         Section 7.13      Entirety. This Agreement and the other Operative
Agreements constitute the entire agreement of the parties hereto with respect to
the subject matter hereof and supersedes all prior understandings and agreements
of such parties.

         Section 7.14      Headings. Section headings in this Agreement are
included herein for convenience of reference only and shall not constitute a
part of this Agreement for any other purpose.

         Section 7.15      LIQUIDITY PROVIDER'S OBLIGATION TO MAKE ADVANCES.
EXCEPT AS EXPRESSLY SET FORTH IN THIS AGREEMENT, THE OBLIGATIONS OF THE
LIQUIDITY PROVIDER TO MAKE ADVANCES HEREUNDER, AND THE BORROWER'S RIGHTS TO
DELIVER NOTICES OF BORROWING REQUESTING THE MAKING OF ADVANCES HEREUNDER, SHALL
BE UNCONDITIONAL AND IRREVOCABLE, AND SHALL BE PAID OR PERFORMED, IN EACH CASE
STRICTLY IN ACCORDANCE WITH THE TERMS OF THIS AGREEMENT.


                                       28
<PAGE>   32


                                                    [REVOLVING CREDIT AGREEMENT]

         IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
duly executed and delivered by their respective officers thereunto duly
authorized as of the date first set forth above.


                               STATE STREET BANK AND TRUST
                               COMPANY OF CONNECTICUT,
                               NATIONAL ASSOCIATION,
                               not in its individual capacity but solely as
                               Subordination Agent and Trustee, as Borrower


                               By: /s/ John G. Correia
                                  ----------------------------------------------
                                  Name:  John G. Correia
                                  Title: Assistant Vice President


                               WESTDEUTSCHE LANDESBANK
                               GIROZENTRALE, NEW YORK BRANCH
                                 as Liquidity Provider


                               By: /s/ Brigitte Thieme
                                  ----------------------------------------------
                                  Name:  Brigitte Thieme
                                  Title: Managing Director


                               By: /s/ Aflred Heynen
                                  ----------------------------------------------
                                  Name:  Alfred Heynen
                                  Title: Associate Director


                                       29
<PAGE>   33
                                                    [REVOLVING CREDIT AGREEMENT]

                                                                      Annex I to
                                                      Revolving Credit Agreement

                      INTEREST ADVANCE NOTICE OF BORROWING

         The undersigned, a duly authorized signatory of the undersigned
borrower (the "Borrower"), hereby certifies to Westdeutsche Landesbank
Girozentrale (the "Liquidity Provider"), with reference to the Revolving Credit
Agreement, dated as of December 14, 2000, between the Borrower and the Liquidity
Provider (the "Liquidity Agreement"; the terms defined therein and not otherwise
defined herein being used herein as therein defined or referenced), that:

                  (1)      The Borrower is the Subordination Agent under the
         Intercreditor Agreement.

                  (2)      The Borrower is delivering this Notice of Borrowing
         for the making of an Interest Advance by the Liquidity Provider to be
         used for the payment of interest on the Class B Certificates which was
         payable on _____________________ in accordance with the terms and
         provisions of the Class B Trust Agreement and the Class B Certificates,
         which Advance is requested to be made on _______________. The Interest
         Advance should be transferred to account __________.

                  (3)      The amount of the Interest Advance requested hereby
         (i) is $__________, to be applied in respect of the payment of interest
         which was due and payable on the Class B Certificates on such
         Distribution Date, (ii) does not include any amount with respect to the
         payment of principal of, or Additional Payments on, the Class A-1
         Certificates, the Class A-2 Certificates, the Class B Certificates or
         the Class C Certificates, or interest on the Class A-1 Certificates,
         the Class A-2 Certificates or the Class C Certificates, (iii) was
         computed in accordance with the provisions of the Class B Certificates,
         the Class B Trust Agreement and the Intercreditor Agreement (a copy of
         which computation is attached hereto as Schedule I), (iv) does not
         exceed the Maximum Available Commitment on the date hereof, and (v) has
         not been and is not the subject of a prior or contemporaneous Notice of
         Borrowing.

                  (4)      Upon receipt by or on behalf of the Borrower of the
         amount requested hereby, (a) the Borrower shall apply the same in
         accordance with the terms of Section 3.6(b) of the Intercreditor
         Agreement, (b) no portion of such amount shall be applied by the
         Borrower for any other purpose and (c) no portion of such amount until
         so applied shall be commingled with other funds held by the Borrower.

         The Borrower hereby acknowledges that, pursuant to the Liquidity
Agreement, the making of the Interest Advance as requested by this Notice of
Borrowing shall automatically


                                      I-1
<PAGE>   34
                                                    [REVOLVING CREDIT AGREEMENT]

reduce, subject to reinstatement in accordance with the terms of the Liquidity
Agreement, the Maximum Available Commitment by an amount equal to the amount of
the Interest Advance requested to be made hereby as set forth in clause (i) of
paragraph (3) of this Notice of Borrowing and such reduction shall automatically
result in corresponding reductions in the amounts available to be borrowed
pursuant to a subsequent Advance.

         IN WITNESS WHEREOF, the Borrower has executed and delivered this Notice
of Borrowing as of the ____ day of ______________, ____.


                            STATE STREET BANK AND TRUST
                            COMPANY OF CONNECTICUT,
                            NATIONAL ASSOCIATION,
                            not in its individual capacity but solely as
                            Subordination Agent, as Borrower


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


                                      I-2


<PAGE>   35


                                                    [REVOLVING CREDIT AGREEMENT]

               SCHEDULE I TO INTEREST ADVANCE NOTICE OF BORROWING

                 [Insert Copy of Computations in accordance with
                     Interest Advance Notice of Borrowing]


                                      I-3
<PAGE>   36


                                                    [REVOLVING CREDIT AGREEMENT]

                                                                     Annex II to
                                                      Revolving Credit Agreement

                    NON-EXTENSION ADVANCE NOTICE OF BORROWING

         The undersigned, a duly authorized signatory of the undersigned
borrower (the "Borrower"), hereby certifies to Westdeutsche Landesbank
Girozentrale (the "Liquidity Provider"), with reference to the Revolving Credit
Agreement, dated as of December 14, 2000, between the Borrower and the Liquidity
Provider (the "Liquidity Agreement"; the terms defined therein and not otherwise
defined herein being used herein as therein defined or referenced), that:

                  (1)      The Borrower is the Subordination Agent under the
         Intercreditor Agreement.

                  (2)      The Borrower is delivering this Notice of Borrowing
         for the making of the Non-Extension Advance by the Liquidity Provider
         to be used for the funding of the Class B Cash Collateral Account in
         accordance with Section 3.6(d) of the Intercreditor Agreement, which
         Advance is requested to be made on __________, ____. The Non-Extension
         Advance should be transferred to ____________.

                  (3)      The amount of the Non-Extension Advance requested
         hereby (i) is $_______________.__, which equals the Maximum Available
         Commitment on the date hereof and is to be applied in respect of the
         funding of the Class B Cash Collateral Account in accordance with
         Section 3.6(d) of the Intercreditor Agreement, (ii) does not include
         any amount with respect to the payment of the principal of, or
         Additional Payments on, the Class A-1 Certificates, the Class A-2
         Certificates, the Class B Certificates or the Class C Certificates, or
         interest on the Class A-1 Certificates, the Class A-2 Certificates or
         the Class C Certificates, (iii) was computed in accordance with the
         provisions of the Class B Certificates, the Class B Trust Agreement and
         the Intercreditor Agreement (a copy of which computation is attached
         hereto as Schedule I), and (iv) has not been and is not the subject of
         a prior or contemporaneous Notice of Borrowing under the Liquidity
         Agreement.

                  (4)      Upon receipt by or on behalf of the Borrower of the
         amount requested hereby, (a) the Borrower will deposit such amount in
         the Class B Cash Collateral Account and apply the same in accordance
         with the terms of Section 3.6(d) of the Intercreditor Agreement, (b) no
         portion of such amount shall be applied by the Borrower for any other
         purpose and (c) no portion of such amount until so applied shall be
         commingled with other funds held by the Borrower.

         The Borrower hereby acknowledges that, pursuant to the Liquidity
Agreement, (A) the making of the Non-Extension Advance as requested by this
Notice of Borrowing shall

                                      II-1

<PAGE>   37
                                                    [REVOLVING CREDIT AGREEMENT]

automatically and irrevocably terminate the obligation of the Liquidity Provider
to make further Advances under the Liquidity Agreement; and (B) following the
making by the Liquidity Provider of the Non-Extension Advance requested by this
Notice of Borrowing, the Borrower shall not be entitled to request any further
Advances under the Liquidity Agreement.

         IN WITNESS WHEREOF, the Borrower has executed and delivered this Notice
of Borrowing as of the ____ day of _________, ____.


                        STATE STREET BANK AND TRUST
                        COMPANY OF CONNECTICUT,
                        NATIONAL ASSOCIATION,
                        not in its individual capacity
                        but solely as Subordination
                        Agent, as Borrower

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


                                      II-2
<PAGE>   38


                                                    [REVOLVING CREDIT AGREEMENT]

                       SCHEDULE I TO NON-EXTENSION ADVANCE
                               NOTICE OF BORROWING
                 [Insert copy of computations in accordance with
                   Non-Extension Advance Notice of Borrowing]


                                      II-3

<PAGE>   39
                                                    [REVOLVING CREDIT AGREEMENT]

                                                                    Annex III to
                                                      Revolving Credit Agreement

                      DOWNGRADE ADVANCE NOTICE OF BORROWING

         The undersigned, a duly authorized signatory of the undersigned
borrower (the "Borrower"), hereby certifies to Westdeutsche Landesbank
Girozentrale (the "Liquidity Provider"), with reference to the Revolving Credit
Agreement dated as of December 14, 2000, between the Borrower and the Liquidity
Provider (the "Liquidity Agreement"; the terms defined therein and not otherwise
defined herein being used herein as therein defined or referenced), that:

                  (1)      The Borrower is the Subordination Agent under the
         Intercreditor Agreement.

                  (2)      The Borrower is delivering this Notice of Borrowing
         for the making of the Downgrade Advance by the Liquidity Provider to be
         used for the funding of the Class B Cash Collateral Account in
         accordance with Section 3.6(c) of the Intercreditor Agreement by reason
         of the downgrading of the relevant rating of the Liquidity Provider
         issued by either Rating Agency below the Threshold Rating, which
         Advance is requested to be made on ______________. The Downgrade
         Advance should be transferred to _____________.

                  (3)      The amount of the Downgrade Advance requested hereby
         (i) is $________, which equals the Maximum Available Commitment on the
         date hereof and is to be applied in respect of the funding of the Class
         B Cash Collateral Account in accordance with Section 3.6(d) of the
         Intercreditor Agreement, (ii) does not include any amount with respect
         to the payment of principal of, or Additional Payments on, the Class
         A-1 Certificates, the Class A-2 Certificates, the Class B Certificates
         or the Class C Certificates or interest on the Class A-1 Certificates,
         the Class A-2 Certificates or the Class C Certificates, (iii) was
         computed in accordance with the provisions of the Class B Certificates,
         the Class B Trust Agreement and the Intercreditor Agreement (a copy of
         which computation is attached hereto as Schedule 1), and (iv) has not
         been and is not the subject of a prior or contemporaneous Notice of
         Borrowing under the Liquidity Agreement.

                  (4)      Upon receipt by or on behalf of the Borrower of the
         amount requested hereby, (a) the Borrower shall deposit such amount in
         the Class B Cash Collateral Account and apply the same in accordance
         with the terms of Section 3.6(d) of the Intercreditor Agreement, (b) no
         portion of such amount shall be applied by the Borrower for any other
         purpose and (c) no portion of such amount until so applied shall be
         commingled with other funds held by the Borrower.


                                     III-1
<PAGE>   40


                                                    [REVOLVING CREDIT AGREEMENT]

         The Borrower hereby acknowledges that, pursuant to the Liquidity
Agreement, (A) the making of the Downgrade Advance as requested by this Notice
of Borrowing shall automatically and irrevocably terminate the obligation of the
Liquidity Provider to make further Advances under the Liquidity Agreement; and
(B) following the making by the Liquidity Provider of the Downgrade Advance
requested by this Notice of Borrowing, the Borrower shall not be entitled to
request any further Advances under the Liquidity Agreement.

         IN WITNESS WHEREOF, the Borrower has executed and delivered this Notice
of Borrowing as of the _____ day of _________, _____.


                                    STATE STREET BANK AND TRUST
                                    COMPANY CONNECTICUT,
                                    NATIONAL ASSOCIATION,
                                    not in its individual capacity but solely as
                                    Subordination Agent, as Borrower


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

                                      III-2

<PAGE>   41


                                                     REVOLVING CREDIT AGREEMENT]

               SCHEDULE I TO DOWNGRADE ADVANCE NOTICE OF BORROWING

                 [Insert Copy of Computations in accordance with
                     Downgrade Advance Notice of Borrowing]


                                      III-3
<PAGE>   42


                                                    [REVOLVING CREDIT AGREEMENT]

                                                                     Annex IV to
                                                      Revolving Credit Agreement


                        FINAL ADVANCE NOTICE OF BORROWING

         The undersigned, a duly authorized signatory of the undersigned
borrower (the "Borrower"), hereby certifies to Westdeutsche Landesbank
Girozentrale (the "Liquidity Provider"), with reference to the Revolving Credit
Agreement, dated as of December 14, 2000, between the Borrower and the Liquidity
Provider (the "Liquidity Agreement"); the terms defined therein and not
otherwise defined herein being used herein as therein defined or referenced),
that:

                  (1)      The Borrower is the Subordination Agent under the
         Intercreditor Agreement.

                  (2)      The Borrower is delivering this Notice of Borrowing
         for the making of the Final Advance by the Liquidity Provider to be
         used for the funding of the Class B Cash Collateral Account in
         accordance with Section 3.6(i) of the Intercreditor Agreement by reason
         of the receipt by the Borrower of a Termination Notice from the
         Liquidity Provider with respect to the Liquidity Agreement, which
         Advance is requested to be made on _______________.

                  (3)      The amount of the Final Advance requested hereby (i)
         is $_____________, which equals the Maximum Available Commitment on the
         date hereof and is to be applied in respect of the funding of the Class
         B Cash Collateral Account in accordance with Section 3.6(i) of the
         Intercreditor Agreement, (ii) does not include any amount with respect
         to the payment of principal of, or Additional Payments on the Class A-1
         Certificates, the Class A-2 Certificates, the Class B Certificates or
         the Class C Certificates, or interest on the Class A-1 Certificates,
         the Class A-2 Certificates or the Class C Certificates, (iii) was
         computed in accordance with the provisions of the Class B Certificates,
         the Class B Trust Agreement and the Intercreditor Agreement (a copy of
         which computation is attached hereto as Schedule I), and (iv) has not
         been and is not the subject of a prior or contemporaneous Notice of
         Borrowing.

                  (4)      Upon receipt by or on behalf of the Borrower of the
         amount requested hereby, (a) the Borrower shall deposit such amount in
         the Class B Cash Collateral Account and apply the same in accordance
         with the terms of Section 3.6(i) of the Intercreditor Agreement, (b) no
         portion of such amount shall be applied by the Borrower for any other
         purpose and (c) no portion of such amount until so applied shall be
         commingled with other funds held by the Borrower.


                                      IV-1
<PAGE>   43


                                                    [REVOLVING CREDIT AGREEMENT]

                  (5)      The Borrower hereby requests that the Advance
         requested hereby be a Base Rate Advance [and that such Base Rate
         Advance be converted into a LIBOR Advance on the third Business Day
         following your receipt of this notice.](1)

                  The Borrower hereby acknowledges that, pursuant to the
Liquidity Agreement, (A) the making of the Final Advance as requested by this
Notice of Borrowing shall automatically and irrevocably terminate the obligation
of the Liquidity Provider to make further Advances under the Liquidity
Agreement; and (B) following the making by the Liquidity Provider of the Final
Advance requested by this Notice of Borrowing, the Borrower shall not be
entitled to request any further Advances under the Liquidity Agreement.

         IN WITNESS WHEREOF, the Borrower has executed and delivered this Notice
of Borrowing as of the _____ day of ___________, _____.


                                    STATE STREET BANK AND TRUST
                                    COMPANY OF CONNECTICUT,
                                    NATIONAL ASSOCIATION,
                                       not in its individual capacity but solely
                                       as Subordination Agent, as Borrower


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

(1) Bracketed language may be included at Borrower's option.


                                      IV-2
<PAGE>   44


                                                    [REVOLVING CREDIT AGREEMENT]

                 SCHEDULE I TO FINAL ADVANCE NOTICE OF BORROWING

                 [Insert Copy of Computations in accordance with
                       Final Advance Notice of Borrowing]


                                      IV-3
<PAGE>   45


                                                    [REVOLVING CREDIT AGREEMENT]

                                                                      Annex V to
                                                      Revolving Credit Agreement

                              NOTICE OF TERMINATION

                                     [Date]

State Street Bank and Trust Company
of Connecticut, National Association,
  as Subordination Agent, as Borrower
225 Asylum Street
Goodwin Square
Hartford, Connecticut 06103

Attention: Corporate Trust Administration

Re:      Revolving Credit Agreement, dated as of December 14, 2000, between
         State Street Bank and Trust Company of Connecticut, National
         Association, as Subordination Agent, as agent and trustee for the
         United Airlines 2000-B Pass Through Trust, as Borrower, and
         Westdeutsche Landesbank Girozentrale, New York Branch (the "Liquidity
         Agreement")

Ladies and Gentlemen:

         You are hereby notified that pursuant to Section 6.01 of the Liquidity
Agreement, by reason of the occurrence of a Liquidity Event of Default and a
Performing Equipment Note Deficiency (each as defined therein), we are giving
this notice to you in order to cause (i) our obligations to make Advances (as
defined therein) under such Liquidity Agreement to terminate on the fifth
Business Day after the date on which you receive this notice and (ii) you to
request a Final Advance under the Liquidity Agreement pursuant to Section 3.6(i)
of the Intercreditor Agreement (as defined in the Liquidity Agreement) as a
consequence of your receipt of this notice.

         THIS NOTICE IS THE "NOTICE OF TERMINATION" PROVIDED FOR UNDER THE
LIQUIDITY AGREEMENT. OUR OBLIGATIONS TO MAKE ADVANCES UNDER THE LIQUIDITY
AGREEMENT SHALL TERMINATE ON THE FIFTH BUSINESS DAY AFTER THE DATE ON WHICH YOU
RECEIVE THIS NOTICE.


                                      V-1
<PAGE>   46
                                                    [REVOLVING CREDIT AGREEMENT]

                                 Very truly yours,

                                 WESTDEUTSCHE LANDESBANK
                                 GIROZENTRALE, NEW YORK BRANCH,
                                 as Liquidity Provider


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


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


cc:   State Street Bank and Trust Company
      of Connecticut, National Association, as Trustee


                                       V-2
<PAGE>   47


                                                    [REVOLVING CREDIT AGREEMENT]

                                                                     Annex VI to
                                                      Revolving Credit Agreement

                    NOTICE OF REPLACEMENT SUBORDINATION AGENT

                                     [Date]

Attention:

Re:      Revolving Credit Agreement, dated as of December 14, 2000, between
         State Street Bank and Trust Company of Connecticut, National
         Association, as Subordination Agent, as agent and trustee for the
         United Airlines 2000-B Pass Through Trust, as Borrower, and
         Westdeutsche Landesbank Girozentrale (the "Liquidity Agreement")

Ladies and Gentlemen:

         For value received, the undersigned hereby irrevocably transfers to:

                                   --------------------------------
                                        [Name of Transferee]

                                   --------------------------------
                                        [Address of Transferee]

all rights and obligations of the undersigned as Borrower and Subordination
Agent under the Liquidity Agreement referred to above. The transferee has
succeeded the undersigned as Borrower and Subordination Agent under the
Intercreditor Agreement referred to in the first paragraph of the Liquidity
Agreement, pursuant to the terms of Section 8.1 of the Intercreditor Agreement.

         By this transfer, all rights of the undersigned as Borrower and
Subordination Agent under the Liquidity Agreement are transferred to the
transferee and the transferee shall hereafter have the sole rights and
obligations as Borrower and Subordination Agent thereunder. The undersigned
shall pay any costs and expenses of such transfer, including, but not limited
to, transfer taxes or governmental charges.


                                      VI-1
<PAGE>   48

                                                    [REVOLVING CREDIT AGREEMENT]

        We ask that this transfer be effective as of ____________, ____.


                               STATE STREET BANK AND TRUST
                               COMPANY OF CONNECTICUT, NATIONAL ASSOCIATION
                               not in its individual capacity but solely as
                               Subordination Agent, as Borrower


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

                                  VI-2