Document:

<PAGE>

                                                                     Exhibit 4.8

                         TRUST SUPPLEMENT NO. 2000-1C-1
                                       TO
                          PASS THROUGH TRUST AGREEMENT

                           Dated as of July 31, 2000

                                    between

                             UNITED AIR LINES, INC.

                                      and

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

                          =========================

                                  $33,130,000

      United Airlines Enhanced Pass Through Certificates, Series 2000-1C-1
<PAGE>

                        TRUST SUPPLEMENT NO.  2000-1C-1

                           Dated as of July 31, 2000

              Enhanced Pass Through Certificates, Series 2000-1C-1

                          ---------------------------

                               Table of Contents
                          ---------------------------
<TABLE>
<CAPTION>
                                                                            Page
                                                                            ----
<S>                      <C>                                                <C>
                         ARTICLE I     DECLARATION OF TRUST

Section 1.01.  Declaration of Trust.......................................   2

                         ARTICLE II    THE CERTIFICATES

Section 2.01.  The Certificates...........................................   2

                         ARTICLE III   DEFINITIONS

Section 3.01.  Definitions................................................   3

                         ARTICLE IV    THE TRUSTEE

Section 4.01.  The Trustee................................................   4

                         ARTICLE V     MISCELLANEOUS PROVISIONS

Section 5.01.  Basic Agreement Ratified...................................   4
Section 5.02.  GOVERNING LAW..............................................   4
Section 5.03.  Execution in Counterparts..................................   4
</TABLE>

                                       i
<PAGE>

Exhibit A   Form of Certificate
Exhibit B   Scheduled Payments of Principal on Class C-1 Certificates

                                       ii
<PAGE>

Exhibit C   Trust Owned Notes, Principal Amounts and Maturities
Exhibit D   Aircraft, Registration Numbers and Maturities
Exhibit E   Note Documents

                                      iii
<PAGE>

                         TRUST SUPPLEMENT NO. 2000-1C-1

          This Trust Supplement No. 2000-1C-1, dated as of July 31, 2000
(herein called the "Trust Supplement"), between United Air Lines, Inc., a
Delaware corporation (the "Company"), and State Street Bank and Trust Company of
Connecticut, National Association, a national banking association (the
"Trustee"), to the Pass Through Trust Agreement, dated as of July 31, 2000 (the
"Basic Agreement"), between the Company and the Trustee.

          WHEREAS, the Basic Agreement, which is unlimited as to the aggregate
principal amount of Certificates that may be issued thereunder, has heretofore
or concurrently herewith been executed and delivered;

          WHEREAS, pursuant to each Owned Aircraft Indenture with respect to the
thirteen Owned Aircraft, United proposes to issue on a recourse basis the United
Equipment Notes to refinance its current indebtedness originally incurred to
finance the Owned Aircraft;

          WHEREAS, pursuant to each Leased Aircraft Indenture with respect to
the six Leased Aircraft, (i) the related Owner Trustees have issued on a
nonrecourse basis Leased Equipment Notes and the current holders of such notes
propose to sell such notes to AFE Trust and (ii) AFE Trust proposes to issue on
a nonrecourse basis the AFE Notes to refinance the current indebtedness
originally incurred to finance the purchase of the Leased Aircraft;

          WHEREAS, pursuant to the 747 Leased Aircraft Indenture with respect to
the one 747 Leased Aircraft, the related Owner Trustee proposes to issue on a
nonrecourse basis the 747 Leased Equipment Notes to refinance its current
indebtedness originally incurred to finance the 747 Leased Aircraft;

          WHEREAS, the Trustee intends to declare the creation of this 2000-1C-1
Trust (the "Class C-1 Trust") for the benefit of the Certificateholders of the
Class C-1 Certificates to be issued in respect of such Class C-1 Trust, and the
initial Certificateholders of the Class C-1 Certificates, as grantors of such
Class C-1 Trust, by their respective acceptances of the Class C-1 Certificates,
shall join in the creation of the Class C-1 Trust with the Trustee;

          WHEREAS, all Certificates to be issued by the Class C-1 Trust will
evidence fractional undivided interests in the Class C-1 Trust created hereby
and will convey no rights, benefits or interests in respect of any property
other than the Trust Property of the Class C-1 Trust;

          WHEREAS, pursuant to the terms and conditions of the Basic Agreement,
as supplemented by this Trust Supplement, and the Note Purchase Agreements, the
Trustee on behalf of the Class C-1 Trust shall purchase the Series C-1 AFE Note
issued by AFE Trust, in which case having the identical interest rate as, and
final maturity dates not later than the final Regular Distribution Date of, the
Class C-1 Certificates issued hereunder and shall hold such Notes in trust for
the benefit of the Class C-1 Certificateholders;
<PAGE>

          WHEREAS, all of the conditions and requirements necessary to make this
Trust Supplement, when duly executed and delivered, a valid, binding and legal
instrument in accordance with its terms and for the purposes herein expressed,
have been done, performed and fulfilled, and the execution and delivery of this
Trust Supplement in the form and with the terms hereof have been in all respects
duly authorized;

          NOW, THEREFORE, in consideration of the premises herein, it is agreed
between the Company and the Trustee as follows:

                                   ARTICLE I
                              DECLARATION OF TRUST

          Section 1.01   Declaration of Trust.  The Trustee hereby declares the
creation of this Class C-1 Trust for the benefit of the Certificateholders of
the Certificates issued hereunder, and the initial Certificateholders, as the
grantors of the Class C-1 Trust, by their respective acceptances of the
Certificates issued hereunder, join in the creation of this Class C-1 Trust with
the Trustee.

                                  ARTICLE II
                               THE CERTIFICATES

          Section 2.01   The Certificates.  There is hereby created a class of
Certificates to be issued under the Agreement, designated and to be
distinguished and known as "United Airlines Enhanced Pass Through Certificates,
Series 2000-1C-1" (the "Class C-1 Certificates").  Each Certificate represents a
Fractional Undivided Interest in the Class C-1 Trust created hereby. The terms
and conditions applicable to the  Class C-1 Certificates are as follows:

          1.  The maximum aggregate principal amount of the Class C-1
     Certificates that shall be authenticated under the Agreement (except for
     Class C-1 Certificates authenticated and delivered pursuant to Sections
     3.04, 3.07 and 3.10 of the Basic Agreement) upon their initial issuance is
     $33,130,000.

          2.  The Cut-off Date is July 31, 2000.

          3.  The Regular Distribution Dates with respect to any payment of
     Scheduled Payments means each January 1 and July 1, commencing on January
     1, 2001 and ending January 1, 2008.

          4.  The Special Distribution Dates with respect to the Class C-1
     Certificates are any Business Day on which a Special Payment is to be
     distributed pursuant to the Agreement.

                                       2
<PAGE>

          5.  The Class C-1 Certificates shall be in the form attached hereto as
     Exhibit A.

          6.  The Scheduled Payments of principal shall be as set forth in
     Exhibit B.

          7.  The proceeds of the Class C-1 Certificates issued under the Class
     C-1 Trust shall be used to purchase the Trust Owned Notes described in
     Exhibit C.

          8.  The Trust Owned Notes described in paragraph 7 relate to the
     Aircraft listed in Exhibit D.

          9.  The related Note Documents are listed in Exhibit E.

          10. The Class C-1 Certificates shall bear the following legend:

          EITHER: (A) THE HOLDER IS NOT ACQUIRING THIS CERTIFICATE OR AN
          INTEREST HEREIN WITH PLAN ASSETS OF ANY PLAN OR AN INDIVIDUAL
          RETIREMENT PLAN SUBJECT TO TITLE I OF THE EMPLOYEE RETIREMENT INCOME
          SECURITY ACT OF 1974, AS AMENDED ("ERISA"), OR SECTION 4975 OF THE
          INTERNAL REVENUE CODE OF 1986, AS AMENDED (THE "CODE"); OR (B) THE
          HOLDER'S PURCHASE AND HOLDING OF THIS CERTIFICATE OR AN INTEREST
          HEREIN IS EXEMPT FROM THE PROHIBITED TRANSACTION RESTRICTIONS OF
          SECTION 406(A) OF ERISA AND SECTION 4975 OF THE CODE BY AN
          ADMINISTRATIVE CLASS PROHIBITED TRANSACTION EXEMPTION GRANTED BY THE
          DEPARTMENT OF LABOR.

                                  ARTICLE III
                                  DEFINITIONS

          Section 3.01   Definitions.  Unless otherwise specified herein,
capitalized terms used herein without definition shall have the respective
meanings specified heretofore in the Basic Agreement or in the Intercreditor
Agreement.

                                  ARTICLE IV
                                  THE TRUSTEE

          Section 4.01   The Trustee.  The Trustee shall not be responsible in
any manner whatsoever for or in respect of the validity or sufficiency of this
Trust Supplement or the due execution hereof by the Company or for or in respect
of the recitals and statements contained herein, all of which recitals and
statements are made solely by the Company.

                                       3
<PAGE>

          Except as herein otherwise provided, no duties, responsibilities or
liabilities are assumed, or shall be construed to be assumed by the Trustee by
reason of this Trust Supplement other than as set forth in the Basic Agreement,
and this Trust Supplement is executed and accepted on behalf of the Trustee,
subject to all the terms and conditions set forth in the Basic Agreement, upon
the effectiveness thereof, as fully to all intents as if the same were herein
set forth at length.

                                   ARTICLE V
                            MISCELLANEOUS PROVISIONS

          Section 5.01   Basic Agreement Ratified.  Except and so far as herein
expressly provided, all of the provisions, terms and conditions of the Basic
Agreement are in all respects ratified and confirmed; and the Basic Agreement
and this Trust Supplement shall be taken, read and construed as one and the same
instrument.

          Section 5.02   GOVERNING LAW.  THIS TRUST SUPPLEMENT AND THE CLASS C-1
CERTIFICATES 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 (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 5.03   Execution in Counterparts.  This Trust Supplement may
be executed in any number of counterparts, each of which shall be an original,
but such counterparts shall together constitute but one and the same instrument.

                                       4
<PAGE>

     IN WITNESS WHEREOF, the Company and the Trustee have caused this Trust
Supplement to be duly executed by their respective officers thereto duly
authorized, as of the day and year first written above.

                              UNITED AIR LINES, INC.

                              By:___________________________

                                 Name:
                                 Title:

                                      S-1
<PAGE>

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

                                    By:_________________________

                                       Name:
                                       Title:

                                      S-2
<PAGE>

                                   EXHIBIT A
                                   ---------

                              FORM OF CERTIFICATE

                             CLASS C-1 CERTIFICATE

                            REGISTERED $33,130,000
                         Fractional Undivided Interest
                                   No. R - 1

     THIS CERTIFICATE HAS NOT BEEN REGISTERED UNDER THE U.S. SECURITIES ACT OF
     1933, AS AMENDED (THE "SECURITIES ACT"), AND ACCORDINGLY, MAY NOT BE
     OFFERED OR SOLD WITHIN THE UNITED STATES OR TO, OR FOR THE ACCOUNT OR
     BENEFIT OF, ANY PERSONS EXCEPT AS SET FORTH IN THE FOLLOWING SENTENCE. BY
     ITS ACQUISITION HEREOF, THE HOLDER (1) REPRESENTS THAT (A) IT IS A
     "QUALIFIED INSTITUTIONAL BUYER" (AS DEFINED IN RULE 144A UNDER THE
     SECURITIES ACT) OR (B) IT IS AN INSTITUTIONAL "ACCREDITED INVESTOR" (AS
     DEFINED IN RULE 501(a)(1), (2), (3) OR (7) OF REGULATION D UNDER THE
     SECURITIES ACT) (AN "INSTITUTIONAL ACCREDITED INVESTOR"); (2) AGREES THAT
     IT WILL NOT WITHIN TWO YEARS AFTER THE LATER OF THE ORIGINAL ISSUANCE OF
     THIS CERTIFICATE OR THE LAST DATE ON WHICH THIS CERTIFICATE WAS HELD BY
     UNITED AIR LINES, INC., THE TRUSTEE OR ANY AFFILIATE OF ANY SUCH PERSON
     RESELL OR OTHERWISE TRANSFER THIS CERTIFICATE EXCEPT (A) TO UNITED AIR
     LINES, INC., (B) TO A QUALIFIED INSTITUTIONAL BUYER IN COMPLIANCE WITH RULE
     144A UNDER THE SECURITIES ACT, (C) TO AN INSTITUTIONAL ACCREDITED INVESTOR
     ACQUIRING $100,000 OR MORE AGGREGATE PRINCIPAL AMOUNT OF SUCH CERTIFICATE
     THAT, PRIOR TO SUCH TRANSFER, FURNISHES TO THE TRUSTEE A SIGNED LETTER
     CONTAINING CERTAIN REPRESENTATIONS AND AGREEMENTS RELATING TO THE
     RESTRICTIONS ON TRANSFER OF THIS CERTIFICATE (THE FORM OF WHICH LETTER CAN
     BE OBTAINED FROM THE TRUSTEE), (D) PURSUANT TO THE EXEMPTION FROM
     REGISTRATION PROVIDED BY RULE 144 UNDER THE SECURITIES ACT (IF AVAILABLE)
     OR (E) PURSUANT TO AN EFFECTIVE REGISTRATION STATEMENT UNDER THE SECURITIES
     ACT; (3) REPRESENTS THAT IT IS A UNITED STATES PERSON WITHIN THE MEANING OF
     SECTION 7701(a)(30) OF THE INTERNAL REVENUE CODE OF 1986, AS AMENDED; AND
     (4) AGREES THAT IT WILL DELIVER TO EACH PERSON TO WHOM THIS

                                      A-1
<PAGE>

     CERTIFICATE IS TRANSFERRED A NOTICE SUBSTANTIALLY TO THE EFFECT OF THIS
     LEGEND. IN CONNECTION WITH ANY TRANSFER OF THIS CERTIFICATE WITHIN TWO
     YEARS AFTER THE LATER OF THE ORIGINAL ISSUANCE OF THIS CERTIFICATE OR THE
     LAST DATE ON WHICH THIS CERTIFICATE WAS HELD BY UNITED AIR LINES, INC., THE
     TRUSTEE OR ANY AFFILIATE OF ANY SUCH PERSONS, THE HOLDER MUST CHECK THE
     APPROPRIATE BOX SET FORTH ON THE REVERSE HEREOF RELATING TO THE MANNER OF
     SUCH TRANSFER AND SUBMIT THIS CERTIFICATE TO THE TRUSTEE. AS USED HEREIN,
     THE TERMS "OFFSHORE TRANSACTION," "UNITED STATES" AND "U.S. PERSON" HAVE
     THE MEANINGS GIVEN TO THEM BY REGULATION S UNDER THE SECURITIES ACT. THE
     PASS THROUGH TRUST AGREEMENT CONTAINS A PROVISION REQUIRING THE TRUSTEE TO
     REFUSE TO REGISTER ANY TRANSFER OF THIS CERTIFICATE IN VIOLATION OF THE
     FOREGOING RESTRICTIONS.

     EITHER:  (A) THE HOLDER IS NOT ACQUIRING THIS CERTIFICATE OR AN INTEREST
     HEREIN WITH PLAN ASSETS OF ANY PLAN OR AN INDIVIDUAL RETIREMENT PLAN
     SUBJECT TO TITLE I OF THE EMPLOYEE RETIREMENT INCOME SECURITY ACT OF 1974,
     AS AMENDED ("ERISA"), OR SECTION 4975 OF THE INTERNAL REVENUE CODE OF 1986,
     AS AMENDED (THE "CODE"); OR (B) THE HOLDER'S PURCHASE AND HOLDING OF THIS
     CERTIFICATE OR AN INTEREST HEREIN IS EXEMPT FROM THE PROHIBITED TRANSACTION
     RESTRICTIONS OF SECTION 406(A) OF ERISA AND SECTION 4975 OF THE CODE BY AN
     ADMINISTRATIVE CLASS PROHIBITED TRANSACTION EXEMPTION GRANTED BY THE
     DEPARTMENT OF LABOR.

                                      A-2
<PAGE>

             UNITED AIRLINES 2000-1C-1 ENHANCED PASS THROUGH TRUST

                         UNITED AIRLINES ENHANCED PASS
                     THROUGH CERTIFICATE, SERIES 2000-1C-1

           Final Expected Regular Distribution Date: January 1, 2008

evidencing a fractional undivided interest in a trust, the property of which
includes a promissory note issued by AFE Trust ("AFE Note").

          THIS CERTIFIES THAT FOUR STAR LEASING, INC., for value received, is
the registered owner of a THIRTY-THREE MILLION, ONE HUNDRED THIRTY THOUSAND
DOLLARS ($33,130,000) Fractional Undivided Interest in the United Airlines 2000-
1C-1 Pass Through Trust (the "Trust") created by State Street Bank and Trust
Company of Connecticut, National Association, as trustee (the "Trustee")
pursuant to a Pass Through Trust Agreement, dated as of July 31, 2000 (the
"Basic Agreement"), as supplemented by Trust Supplement No. 2000-1C-1
(collectively, the "Agreement") between the Trustee and United Air Lines, Inc.,
a Delaware corporation (the "Company"), a summary of certain of the pertinent
provisions of which is set forth below. To the extent not otherwise defined
herein, the capitalized terms used herein have the meanings assigned to them in
the Agreement. This Certificate is one of the duly authorized Certificates
designated as "United Airlines Enhanced Pass Through Certificates, Series 2000-
1C-1" (the "Certificates"). This Certificate is issued under and is subject to
the terms, provisions and conditions of the Agreement.

          By virtue of its acceptance hereof, the Certificateholder of this
Certificate assents to and agrees to be bound by the provisions of the
Agreement, the Intercreditor Agreement and the AFE Note Purchase Agreement. The
property of the Trust includes (i) the AFE Note and all monies at any time paid
thereon and all monies due and to become due thereunder, (ii) funds from time to
time deposited in the related Escrow Account, the related Certificate Account
and the related Special Payments Account and (iii) all rights of such Trust and
the Trustee, on behalf of such Trust, under the Intercreditor Agreement and the
AFE Note Purchase Agreement, including all rights to receive certain payments
thereunder and all monies paid to such Trustee on behalf of such Trust pursuant
to the Intercreditor Agreement and the AFE Note Purchase Agreement (the "Trust
Property"). Each issue of the Trust Owned Notes is secured indirectly by, among
other things, a security interest in the Aircraft leased to the Company.

          The Certificates represent Fractional Undivided Interests in the
Trust, all other trusts of the same class and the Trust Property, and have no
rights, benefits or interest in respect of any assets or property of any trust
of another class.

          Interest applicable to this Certificate will be payable at a floating
rate equal to the Eurodollar Rate plus 0.90%.

                                      A-3
<PAGE>

          Subject to and in accordance with the terms of the Agreement, the
Intercreditor Agreement and the AFE Note Purchase Agreement, from and to the
extent of funds then available to the Trustee, there shall be distributed on
each January 1 and July 1 (a "Regular Distribution Date"), commencing on January
1, 2001, to the Person in whose name this Certificate is registered at the close
of business on the 15th day preceding such Regular Distribution Date, an amount
in respect of the Scheduled Payments on the Trust Owned Notes due on such
Regular Distribution Date, the receipt of which has been confirmed by the
Trustee, equal to the product of the percentage interest in the Trust evidenced
by this Certificate and an amount equal to the sum of such Scheduled Payments.
Subject to and in accordance with the terms of the Agreement, the Intercreditor
Agreement and the AFE Note Purchase Agreement, if Special Payments on the Trust
Owned Notes are received by the Trustee, from funds then available to the
Trustee, there shall be distributed on the applicable Special Distribution Date,
to the Person in whose name this Certificate is registered at the close of
business on the 15th day preceding the Special Distribution Date, an amount in
respect of such Special Payments on the Trust Owned Notes, the receipt of which
has been confirmed by the Trustee, equal to the product of the percentage
interest in the Trust (or, if more than one trust of like class, all such
trusts) evidenced by this Certificate and an amount equal to the sum of such
Special Payments so received. If a Regular Distribution Date or Special
Distribution Date is not a Business Day, distribution shall be made on the next
Business Day with the same force and effect as if made on such Regular
Distribution Date or Special Distribution Date and interest shall accrue during
the intervening period. The Trustee shall mail notice of each Special Payment
and the Special Distribution Date therefor to the Certificateholder of this
Certificate.

         Except as otherwise provided in the Agreement and notwithstanding the
above, the final distribution on this Certificate shall be made after notice
mailed by the Trustee of the pendency of such distribution and only upon
presentation and surrender of this Certificate at the office or agency of the
Trustee specified in such notice.

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

          Reference is hereby made to the further provisions of this Certificate
set forth in the reverse hereof, which further provisions shall for all purposes
have the same effect as if set forth at this place.

          Unless the certificate of authentication hereon has been executed by
the Trustee, by manual signature, this Certificate shall not be entitled to any
benefit under the Agreement or be valid or obligatory for any purpose.

                                      A-4
<PAGE>

          IN WITNESS WHEREOF, the Trustee, on behalf of the Issuer and not in
its individual capacity, has caused this Certificate to be duly executed.

                                       UNITED AIRLINES 2000-1C-1 PASS
                                       THROUGH TRUST

                                       By:  STATE STREET BANK AND TRUST COMPANY
                                       OF CONNECTICUT, NATIONAL ASSOCIATION, not
                                       in its individual capacity but solely as
                                       Trustee

Dated: __________________              By: __________________________________

                                          Name: _____________________________

                                          Title: ____________________________

                                      A-5
<PAGE>

                    TRUSTEE'S CERTIFICATE OF AUTHENTICATION

     This is one of the Certificates referred to in the within-mentioned Trust
Agreement.

State Street Bank and Trust Company       State Street Bank and Trust Company of
of Connecticut, National Association,     Connecticut, National Association,
not in its individual capacity but        not in its individual capacity but
solely as Trustee                         solely as Trustee

By:______________________                 By:___________________________
                                               Authenticating Agent

                                          By:___________________________

                                      A-6
<PAGE>

                           [REVERSE OF CERTIFICATE]

          The Certificates do not represent a direct obligation of, or an
obligation guaranteed by, or an interest in, the Company or the Trustee or any
of their Affiliates. The Certificates are limited in right or payment, all as
more specifically set forth on the face hereof and in the Agreement. All
payments or distributions made to Certificateholders under the Agreement shall
be made only from the Trust Property and only to the extent that the Trustee
shall have sufficient income or proceeds from the Trust Property to make such
payments in accordance with the terms of the Agreement. Each Certificateholder
of this Certificate, by its acceptance hereof, agrees that it shall look solely
to the income and proceeds from the Trust Property to the extent available for
distribution to such Certificateholder as provided in the Agreement. This
Certificate does not purport to summarize the Agreement and reference is made to
the Agreement for information with respect to the interests, rights, benefits,
obligations, proceeds and duties evidenced hereby. A copy of the Agreement may
be examined during normal business hours at the principal office of the Trustee,
and at such other places, if any, designated by the Trustee, by any
Certificateholder upon request.

          The Agreement permits, with certain exceptions therein provided, the
amendment thereof and the modification of the rights and obligations of the
Company and the rights of the Certificateholders under the Agreement at any time
by the Company and the Trustee with the consent of the Certificateholders
holding Certificates evidencing Fractional Cumulative Interests aggregating not
less than a majority in interest in the Trust. Any such consent by the
Certificateholder of this Certificate shall be conclusive and binding on such
Certificateholder and upon all future Certificateholders of this Certificate and
of any Certificate issued upon the transfer hereof or in exchange hereof or in
lieu hereof whether or not notation of such consent is made upon this
Certificate. The Agreement also permits the amendment thereof, in certain
limited circumstances, without the consent of the Certificateholders of any of
the Certificates.

          As provided in the Agreement and subject to certain limitations
therein set forth, the transfer of this Certificate is registrable in the
Register upon surrender of this Certificate for registration of transfer at the
offices or agencies maintained by the Trustee in its capacity as Registrar, or
by any successor Registrar, at its Corporate Trust Office, duly endorsed or
accompanied by a written instrument of transfer in form satisfactory to the
Trustee and the Registrar duly executed by the Certificateholder hereof or such
Certificateholder's attorney duly authorized in writing, and thereupon one or
more new Certificates of authorized denominations evidencing the same aggregate
Fractional Undivided Interest in the Trust shall be issued to the designated
transferee or transferees.

          The Certificates are issuable only as registered Certificates without
coupons in minimum denominations of $1,000 Fractional Undivided Interest and
integral multiples of $1,000 in excess thereof. As provided in the Agreement and
subject to certain limitations therein set forth, the Certificates are
exchangeable for new Certificates of authorized denominations evidencing the

                                      A-7
<PAGE>

same aggregate Fractional Undivided Interest in the Trust, as requested by the
Certificateholder surrendering the same.

          No service charge shall be made for any such registration of transfer
or exchange, but the Trustee shall require payment by the Certificateholder of a
sum sufficient to cover any tax or governmental charge payable in connection
therewith.

          The Trustee, the Registrar, and any agent of the Trustee or the
Registrar may treat the person in whose name this Certificate is registered as
the owner hereof for all purposes, and neither the Trustee, the Registrar, nor
any such agent shall be affected by any notice to the contrary.

          The obligations and responsibilities created by the Agreement and the
Trust created thereby shall terminate upon the distribution to
Certificateholders of all amounts required to be distributed to them pursuant to
the Agreement and the disposition of all property held as part of the Trust
Property.

                                      A-8
<PAGE>

                            FORM OF TRANSFER NOTICE

          FOR VALUE RECEIVED the undersigned registered holder hereby sell(s),
assign(s) and transfer(s) unto

Insert Taxpayer Identification No.

________________________________________________________________________________
please print or typewrite name and address including zip code of assignee

--------------------------------------------------------------------------------
the within Certificate and all rights thereunder, hereby irrevocably
constituting and appointing

--------------------------------------------------------------------------------
attorney to transfer said Certificate on the books of the Trustee with full
power of substitution in the premises.

Date:                                       [Name of Transferor]

                                            ____________________________________

                              NOTE:  The signature must correspond with the name
                              as written upon the face of the within-mentioned
                              instrument in every particular, without alteration
                              or any change whatsoever.

Signature Guarantee:_____________

                                      A-9
<PAGE>

                         MANNER OF TRANSFER

     This form shall be completed if this Certificate or an interest herein is
transferred within two years after the later of the original issuance of the
certificate or the last date on which this certificate was held by United Air
Lines, Inc., the Trustee or any Affiliate of any such Persons.  This form shall
be delivered to the Trustee upon completion.

     The Holder of the United Airlines Enhanced Pass Through Certificate, Series
2000-1C-1 hereby transfers a beneficial interest in the aforesaid certificate to
________________, in one of the following permissible transfers:

      [ ]  To United Air Lines, Inc.

      [ ]  To a qualified institutional buyer in compliance with Rule 144A under
           the Securities Act

      [ ]  To an institutional accredited investor acquiring $100,000 or more
           aggregate principal amount of this Certificate that has, prior to
           this transfer, furnished to the Trustee a signed letter containing
           certain representations and agreements relating to the restrictions
           on transfer of this Certificate

      [ ]  Pursuant to the exemption from registration provided by Rule 144
           under the Securities Act (if available)

      [ ]   Pursuant to an effective registration statement under the Securities
            Act

                                      A-10
<PAGE>

                                   EXHIBIT B
                                   ---------

                        SCHEDULED PAYMENTS OF PRINCIPAL
                           ON CLASS C-1 CERTIFICATES

     Payment Date              Principal Payment
     ------------              -----------------

                                      B-1
<PAGE>

                                   EXHIBIT C
                                   ---------

                               TRUST OWNED NOTES
                        PRINCIPAL AMOUNTS AND MATURITIES

  Trust Owned Notes           Principal Amount                      Maturity
  -----------------           ----------------                      --------

                                      C-1
<PAGE>

                                   EXHIBIT D
                                   ---------

                 AIRCRAFT, REGISTRATION NUMBERS AND MATURITIES

                                         Aircraft
                                       Registration
  Aircraft                                Number                       Maturity
  --------                             ------------                    --------

                                      D-1
<PAGE>

                                   EXHIBIT E
                                   ---------

                                 NOTE DOCUMENTS

<TABLE>
<CAPTION>
                      Aircraft
Aircraft            Registration
Leased                 Number     Note Document
----------------    ------------  -------------
<S>                 <C>           <C>

Boeing 757-222      N567UA        AFE Note Purchase Agreement
                                  AFE Indenture
                                  Each Confirmation
                                  AFE Note, Series A-1
                                  AFE Note, Series A-2
                                  AFE Note, Series B
                                  AFE Note, Series C

Boeing 757-222      N568UA        AFE Note Purchase Agreement
                                  AFE Indenture
                                  Each Confirmation
                                  AFE Note, Series A-1
                                  AFE Note, Series A-2
                                  AFE Note, Series B
                                  AFE Note, Series C

Boeing 757-222      N569UA        AFE Note Purchase Agreement
                                  AFE Indenture
                                  Each Confirmation
                                  AFE Note, Series A-1
                                  AFE Note, Series A-2
                                  AFE Note, Series B
                                  AFE Note, Series C

Boeing 757-222      N570UA        AFE Note Purchase Agreement
                                  AFE Indenture
                                  Each Confirmation
                                  AFE Note, Series A-1
                                  AFE Note, Series A-2
                                  AFE Note, Series B
                                  AFE Note, Series C

Boeing 757-222      N571UA        AFE Note Purchase Agreement
                                  AFE Indenture
</TABLE>
                                E-1

<PAGE>

                               Each Confirmation
<TABLE>
<CAPTION>

                    Aircraft
Aircraft          Registration
Leased               Number              Note Document
------            ------------           -------------
<S>               <C>                 <C>
                                      AFE Note, Series A-1
                                      AFE Note, Series A-2
                                      AFE Note, Series B
                                      AFE Note, Series C

Boeing 757-222    N572UA              AFE Note Purchase Agreement
                                      AFE Indenture
                                      Each Confirmation
                                      AFE Note, Series A-1
                                      AFE Note, Series A-2
                                      AFE Note, Series B
                                      AFE Note, Series C
</TABLE>

                                      E-2<PAGE>
                                                                     Exhibit 4.9

                        TRUST SUPPLEMENT NO. 2000-1C-2
                                      TO
                         PASS THROUGH TRUST AGREEMENT

                           Dated as of July 31, 2000

                                    between

                            UNITED AIR LINES, INC.

                                      and

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

                              ===================

                                  $86,401,000

     United Airlines Enhanced Pass Through Certificates, Series 2000-1C-2

<PAGE>

                        TRUST SUPPLEMENT NO. 2000-1C-2

                           Dated as of July 31, 2000

             Enhanced Pass Through Certificates, Series 2000-1C-2

                               ----------------

                               Table of Contents

                               ----------------

<TABLE>
<CAPTION>
                                                                            Page
                                                                            ----
<C>            <S>                                                          <C>
                        ARTICLE I  DECLARATION OF TRUST
Section 1.01.  Declaration of Trust.......................................     2

                          ARTICLE II  THE CERTIFICATES
Section 2.01.  The Certificates...........................................     2

                            ARTICLE III  DEFINITIONS
Section 3.01.  Definitions................................................     3

                            ARTICLE IV  THE TRUSTEE
Section 4.01.  The Trustee................................................     4

                      ARTICLE V  MISCELLANEOUS PROVISIONS
Section 5.01.  Basic Agreement Ratified...................................     4
Section 5.02.  GOVERNING LAW..............................................     4
Section 5.03.  Execution in Counterparts..................................     4
</TABLE>

                                       i
<PAGE>

Exhibit A   Form of Certificate
Exhibit B   Scheduled Payments of Principal on Class C-2 Certificates

                                      ii
<PAGE>

Exhibit C   Trust Owned Notes, Principal Amounts and Maturities
Exhibit D   Aircraft, Registration Numbers and Maturities
Exhibit E   Note Documents

                                      iii
<PAGE>

                        TRUST SUPPLEMENT NO. 2000-1C-2

          This Trust Supplement No. 2000-1C-2, dated as of July 31, 2000 (herein
called the "Trust Supplement"), between United Air Lines, Inc., a Delaware
corporation (the "Company"), and State Street Bank and Trust Company of
Connecticut, National Association, a national banking association (the
"Trustee"), to the Pass Through Trust Agreement, dated as of July 31, 2000 (the
"Basic Agreement"), between the Company and the Trustee.

          WHEREAS, the Basic Agreement, which is unlimited as to the aggregate
principal amount of Certificates that may be issued thereunder, has heretofore
or concurrently herewith been executed and delivered;

          WHEREAS, pursuant to each Owned Aircraft Indenture with respect to the
thirteen Owned Aircraft, United proposes to issue on a recourse basis the United
Equipment Notes to refinance its current indebtedness originally incurred to
finance the Owned Aircraft;

          WHEREAS, pursuant to each Leased Aircraft Indenture with respect to
the six Leased Aircraft, (i) the related Owner Trustees have issued on a
nonrecourse basis Leased Equipment Notes and the current holders of such notes
propose to sell such notes to AFE Trust and (ii) AFE Trust proposes to issue on
a nonrecourse basis the AFE Notes to refinance the current indebtedness
originally incurred to finance the purchase of the Leased Aircraft;

          WHEREAS, pursuant to the 747 Leased Aircraft Indenture with respect to
the one 747 Leased Aircraft, the related Owner Trustee proposes to issue on a
nonrecourse basis the 747 Leased Equipment Notes to refinance its current
indebtedness originally incurred to finance the 747 Leased Aircraft;

          WHEREAS, the Trustee intends to declare the creation of this 2000-1C-2
Trust (the "Class C-2 Trust") for the benefit of the Certificateholders of the
Class C-2 Certificates to be issued in respect of such Class C-2 Trust, and the
initial Certificateholders of the Class C-2 Certificates, as grantors of such
Class C-2 Trust, by their respective acceptances of the Class C-2 Certificates,
shall join in the creation of the Class C-2 Trust with the Trustee;

          WHEREAS, all Certificates to be issued by the Class C-2 Trust will
evidence fractional undivided interests in the Class C-2 Trust created hereby
and will convey no rights, benefits or interests in respect of any property
other than the Trust Property of the Class C-2 Trust;

          WHEREAS, pursuant to the terms and conditions of the Basic Agreement,
as supplemented by this Trust Supplement, and the Note Purchase Agreements, the
Trustee on behalf of the Class C-2 Trust shall purchase the Series C-2 United
Equipment Notes issued by the Company and the Series C-2 747 Leased Equipment
Note issued by the Owner Trustee under the 747 Leased Aircraft Indenture, in
each case having the identical interest rate as, and final maturity dates not
later than the final Regular Distribution Date of, the Class C-2 Certificates
issued hereunder and shall hold such Notes in trust for the benefit of the Class
C-2 Certificateholders;

<PAGE>

          WHEREAS, all of the conditions and requirements necessary to make this
Trust Supplement, when duly executed and delivered, a valid, binding and legal
instrument in accordance with its terms and for the purposes herein expressed,
have been done, performed and fulfilled, and the execution and delivery of this
Trust Supplement in the form and with the terms hereof have been in all respects
duly authorized;

          NOW, THEREFORE, in consideration of the premises herein, it is agreed
between the Company and the Trustee as follows:

                                   ARTICLE I
                              DECLARATION OF TRUST

          Section 1.01   Declaration of Trust.  The Trustee hereby declares the
creation of this Class C-2 Trust for the benefit of the Certificateholders of
the Certificates issued hereunder, and the initial Certificateholders, as the
grantors of the Class C-2 Trust, by their respective acceptances of the
Certificates issued hereunder, join in the creation of this Class C-2 Trust with
the Trustee.

                                  ARTICLE II
                               THE CERTIFICATES

          Section 2.01   The Certificates.  There is hereby created a class of
Certificates to be issued under the Agreement, designated and to be
distinguished and known as "United Airlines Enhanced Pass Through Certificates,
Series 2000-1C-2" (the "Class C-2 Certificates").  Each Certificate represents a
Fractional Undivided Interest in the Class C-1 Trust created hereby.  The terms
and conditions applicable to the Class C-2 Certificates are as follows:

          1.  The maximum aggregate principal amount of the Class C-2
     Certificates that shall be authenticated under the Agreement (except for
     Class C-2 Certificates authenticated and delivered pursuant to Sections
     3.04, 3.07 and 3.10 of the Basic Agreement) upon their initial issuance is
     $86,401,000.

          2.  The Cut-off Date is July 31, 2000.

          3.  The Regular Distribution Dates with respect to any payment of
     Scheduled Payments means each January 1 and July 1, commencing on January
     1, 2001 and ending January 1, 2014.

          4.  The Special Distribution Dates with respect to the Class C-2
     Certificates are any Business Day on which a Special Payment is to be
     distributed pursuant to the Agreement.
<PAGE>

          5.  The Class C-2 Certificates shall be in the form attached hereto as
     Exhibit A.

          6.  The Scheduled Payments of principal shall be as set forth in
     Exhibit B.

          7.  The proceeds of the Class C-2 Certificates issued under the Class
     2000-1C-2 Trust shall be used to purchase the Trust Owned Notes described
     in Exhibit C.

          8.  The Trust Owned Notes described in paragraph 7 relate to the
     Aircraft listed in Exhibit D.

          9.  The related Note Documents are listed in Exhibit E.

          10. The Class C-2 Certificates shall bear the following legend:

          EITHER: (A) THE HOLDER IS NOT ACQUIRING THIS CERTIFICATE OR AN
          INTEREST HEREIN WITH PLAN ASSETS OF ANY PLAN OR AN INDIVIDUAL
          RETIREMENT PLAN SUBJECT TO TITLE I OF THE EMPLOYEE RETIREMENT INCOME
          SECURITY ACT OF 1974, AS AMENDED ("ERISA"), OR SECTION 4975 OF THE
          INTERNAL REVENUE CODE OF 1986, AS AMENDED (THE "CODE"); OR (B) THE
          HOLDER'S PURCHASE AND HOLDING OF THIS CERTIFICATE OR AN INTEREST
          HEREIN  IS EXEMPT FROM THE PROHIBITED TRANSACTION RESTRICTIONS OF
          SECTION 406(A) OF ERISA AND SECTION 4975 OF THE CODE BY AN
          ADMINISTRATIVE CLASS PROHIBITED TRANSACTION EXEMPTION GRANTED BY THE
          DEPARTMENT OF LABOR.

                                  ARTICLE III
                                  DEFINITIONS

          Section 3.01  Definitions.  Unless otherwise specified herein,
capitalized terms used herein without definition shall have the respective
meanings specified heretofore in the Basic Agreement or in the Intercreditor
Agreement.

                                  ARTICLE IV
                                  THE TRUSTEE

          Section 4.01  The Trustee.  The Trustee shall not be responsible in
any manner whatsoever for or in respect of the validity or sufficiency of this
Trust Supplement or the due execution hereof by the Company or for or in respect
of the recitals and statements contained herein, all of which recitals and
statements are made solely by the Company.

                                       3
<PAGE>

          Except as herein otherwise provided, no duties, responsibilities or
liabilities are assumed, or shall be construed to be assumed by the Trustee by
reason of this Trust Supplement other than as set forth in the Basic Agreement,
and this Trust Supplement is executed and accepted on behalf of the Trustee,
subject to all the terms and conditions set forth in the Basic Agreement, upon
the effectiveness thereof, as fully to all intents as if the same were herein
set forth at length.

                                   ARTICLE V
                            MISCELLANEOUS PROVISIONS

          Section 5.01  Basic Agreement Ratified.  Except and so far as herein
expressly provided, all of the provisions, terms and conditions of the Basic
Agreement are in all respects ratified and confirmed; and the Basic Agreement
and this Trust Supplement shall be taken, read and construed as one and the same
instrument.

          Section 5.02  GOVERNING LAW.  THIS TRUST SUPPLEMENT AND THE CLASS C-2
CERTIFICATES 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 (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 5.03  Execution in Counterparts.  This Trust Supplement may
be executed in any number of counterparts, each of which shall be an original,
but such counterparts shall together constitute but one and the same instrument.

                                       4
<PAGE>

     IN WITNESS WHEREOF, the Company and the Trustee have caused this Trust
Supplement to be duly executed by their respective officers thereto duly
authorized, as of the day and year first written above.

                              UNITED AIR LINES, INC.

                              By:___________________________

                                 Name:
                                 Title:

                                      S-1
<PAGE>

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

                                    By:________________________________

                                          Name:
                                          Title:

                                      S-2
<PAGE>

                                   EXHIBIT A
                                   ---------

                              FORM OF CERTIFICATE

                             CLASS C-2 CERTIFICATE

                            REGISTERED $86,401,000
                         Fractional Undivided Interest
                                    No. R-1

THIS CERTIFICATE HAS NOT BEEN REGISTERED UNDER THE U.S. SECURITIES ACT OF 1933,
AS AMENDED (THE "SECURITIES ACT"), AND ACCORDINGLY, MAY NOT BE OFFERED OR SOLD
WITHIN THE UNITED STATES OR TO, OR FOR THE ACCOUNT OR BENEFIT OF, ANY PERSONS
EXCEPT AS SET FORTH IN THE FOLLOWING SENTENCE. BY ITS ACQUISITION HEREOF, THE
HOLDER (1) REPRESENTS THAT (A) IT IS A "QUALIFIED INSTITUTIONAL BUYER" (AS
DEFINED IN RULE 144A UNDER THE SECURITIES ACT) OR (B) IT IS AN INSTITUTIONAL
"ACCREDITED INVESTOR" (AS DEFINED IN RULE 501(a)(1), (2), (3) OR (7) OF
REGULATION D UNDER THE SECURITIES ACT) (AN "INSTITUTIONAL ACCREDITED INVESTOR");
(2) AGREES THAT IT WILL NOT WITHIN TWO YEARS AFTER THE LATER OF THE ORIGINAL
ISSUANCE OF THIS CERTIFICATE OR THE LAST DATE ON WHICH THIS CERTIFICATE WAS HELD
BY UNITED AIR LINES, INC., THE TRUSTEE OR ANY AFFILIATE OF ANY SUCH PERSON
RESELL OR OTHERWISE TRANSFER THIS CERTIFICATE EXCEPT (A) TO UNITED AIR LINES,
INC., (B) TO A QUALIFIED INSTITUTIONAL BUYER IN COMPLIANCE WITH RULE 144A UNDER
THE SECURITIES ACT, (C) TO AN INSTITUTIONAL ACCREDITED INVESTOR ACQUIRING
$100,000 OR MORE AGGREGATE PRINCIPAL AMOUNT OF SUCH CERTIFICATE THAT, PRIOR TO
SUCH TRANSFER, FURNISHES TO THE TRUSTEE A SIGNED LETTER CONTAINING CERTAIN
REPRESENTATIONS AND AGREEMENTS RELATING TO THE RESTRICTIONS ON TRANSFER OF THIS
CERTIFICATE (THE FORM OF WHICH LETTER CAN BE OBTAINED FROM THE TRUSTEE), (D)
PURSUANT TO THE EXEMPTION FROM REGISTRATION PROVIDED BY RULE 144 UNDER THE
SECURITIES ACT (IF AVAILABLE) OR (E) PURSUANT TO AN EFFECTIVE REGISTRATION
STATEMENT UNDER THE SECURITIES ACT; (3) REPRESENTS THAT IT IS A UNITED STATES
PERSON WITHIN THE MEANING OF SECTION 7701(a)(30) OF THE INTERNAL REVENUE CODE OF
1986, AS AMENDED; AND (4) AGREES THAT IT WILL DELIVER TO EACH PERSON TO WHOM
THIS CERTIFICATE IS TRANSFERRED A NOTICE SUBSTANTIALLY TO THE EFFECT OF THIS
LEGEND. IN CONNECTION WITH ANY TRANSFER OF THIS CERTIFICATE WITHIN TWO YEARS
AFTER THE LATER OF THE ORIGINAL ISSUANCE OF THIS

                                      A-1
<PAGE>

CERTIFICATE OR THE LAST DATE ON WHICH THIS CERTIFICATE WAS HELD BY UNITED AIR
LINES, INC., THE TRUSTEE OR ANY AFFILIATE OF ANY SUCH PERSONS, THE HOLDER MUST
CHECK THE APPROPRIATE BOX SET FORTH ON THE REVERSE HEREOF RELATING TO THE MANNER
OF SUCH TRANSFER AND SUBMIT THIS CERTIFICATE TO THE TRUSTEE. AS USED HEREIN, THE
TERMS "OFFSHORE TRANSACTION," "UNITED STATES" AND "U.S. PERSON" HAVE THE
MEANINGS GIVEN TO THEM BY REGULATION S UNDER THE SECURITIES ACT. THE PASS
THROUGH TRUST AGREEMENT CONTAINS A PROVISION REQUIRING THE TRUSTEE TO REFUSE TO
REGISTER ANY TRANSFER OF THIS CERTIFICATE IN VIOLATION OF THE FOREGOING
RESTRICTIONS.

EITHER: (A) THE HOLDER IS NOT ACQUIRING THIS CERTIFICATE OR AN INTEREST HEREIN
WITH PLAN ASSETS OF ANY PLAN OR AN INDIVIDUAL RETIREMENT PLAN SUBJECT TO TITLE I
OF THE EMPLOYEE RETIREMENT INCOME SECURITY ACT OF 1974, AS AMENDED ("ERISA"), OR
SECTION 4975 OF THE INTERNAL REVENUE CODE OF 1986, AS AMENDED (THE "CODE"); OR
(B) THE HOLDER'S PURCHASE AND HOLDING OF THIS CERTIFICATE OR AN INTEREST HEREIN
IS EXEMPT FROM THE PROHIBITED TRANSACTION RESTRICTIONS OF SECTION 406(A) OF
ERISA AND SECTION 4975 OF THE CODE BY AN ADMINISTRATIVE CLASS PROHIBITED
TRANSACTION EXEMPTION GRANTED BY THE DEPARTMENT OF LABOR.

                                      A-2
<PAGE>

             UNITED AIRLINES 2000-1C-2 ENHANCED PASS THROUGH TRUST

      UNITED AIRLINES ENHANCED PASS THROUGH CERTIFICATE, SERIES 2000-1C-2

           Final Expected Regular Distribution Date: January 1, 2014

evidencing a fractional undivided interest in a trust, the property of which
includes certain equipment notes each secured by an Aircraft owned by or leased
to United Air Lines, Inc.

     THIS CERTIFIES THAT FOUR STAR LEASING, INC., for value received, is the
registered owner of a EIGHTY-SIX MILLION, FOUR HUNDRED ONE THOUSAND DOLLARS
($86,401,000) Fractional Undivided Interest in the United Airlines 2000-1C-2
Pass Through Trust (the "Trust") created by State Street Bank and Trust Company
of Connecticut, National Association, as trustee (the "Trustee") pursuant to a
Pass Through Trust Agreement, dated as of July 31, 2000 (the "Basic Agreement"),
as supplemented by Trust Supplement No. 2000-1C-2 (collectively, the
"Agreement") between the Trustee and United Air Lines, Inc., a Delaware
corporation (the "Company"), a summary of certain of the pertinent provisions of
which is set forth below. To the extent not otherwise defined herein, the
capitalized terms used herein have the meanings assigned to them in the
Agreement. This Certificate is one of the duly authorized Certificates
designated as "United Airlines Enhanced Pass Through Certificates, Series 2000-
1C-2" (the "Certificates"). This Certificate is issued under and is subject to
the terms, provisions and conditions of the Agreement.

     By virtue of its acceptance hereof, the Certificateholder of this
Certificate assents to and agrees to be bound by the provisions of the
Agreement, the Intercreditor Agreement and the 747 Leased Equipment Note
Purchase Agreement and the United Equipment Note Purchase Agreement. The
property of the Trust includes (i) certain Equipment Notes and all monies at any
time paid thereon and all monies due and to become due thereunder, (ii) funds
from time to time deposited in the related Escrow Account, the related
Certificate Account and the related Special Payments Account and (iii) all
rights of such Trust and the Trustee, on behalf of such Trust, under the
Intercreditor Agreement and the Note Purchase Agreements, including all rights
to receive certain payments thereunder and all monies paid to such Trustee on
behalf of such Trust pursuant to the Intercreditor Agreement and the 747 Leased
Equipment Note Purchase Agreement and the United Equipment Note Purchase
Agreement (the "Trust Property"). Each issue of the Trust Owned Notes is secured
by, among other things, a security interest directly or indirectly in the
Aircraft leased to or owned by the Company.

     The Certificates represent Fractional Undivided Interests in the Trust, all
other trusts of the same class and the Trust Property, and have no rights,
benefits or interest in respect of any assets or property of any trust of
another class.

     Interest applicable to this Certificate will be payable at a rate equal to
8.450%.

                                      A-3
<PAGE>

     Subject to and in accordance with the terms of the Agreement, the
Intercreditor Agreement and the 747 Leased Equipment Note Purchase Agreement and
the United Equipment Note Purchase Agreement, from and to the extent of funds
then available to the Trustee, there shall be distributed on each January 1 and
July 1 (a "Regular Distribution Date"), commencing on January 1, 2001, to the
Person in whose name this Certificate is registered at the close of business on
the 15th day preceding such Regular Distribution Date, an amount in respect of
the Scheduled Payments on the Trust Owned Notes due on such Regular Distribution
Date, the receipt of which has been confirmed by the Trustee, equal to the
product of the percentage interest in the Trust evidenced by this Certificate
and an amount equal to the sum of such Scheduled Payments. Subject to and in
accordance with the terms of the Agreement, the Intercreditor Agreement, the 747
Leased Equipment Note Purchase Agreement and the United Equipment Note Purchase
Agreement, if Special Payments on the Trust Owned Notes are received by the
Trustee, from funds then available to the Trustee, there shall be distributed on
the applicable Special Distribution Date, to the Person in whose name this
Certificate is registered at the close of business on the 15th day preceding the
Special Distribution Date, an amount in respect of such Special Payments on the
Trust Owned Notes, the receipt of which has been confirmed by the Trustee, equal
to the product of the percentage interest in the Trust evidenced by this
Certificate and an amount equal to the sum of such Special Payments so received.
If a Regular Distribution Date or Special Distribution Date is not a Business
Day, distribution shall be made on the next Business Day with the same force and
effect as if made on such Regular Distribution Date or Special Distribution Date
and interest shall accrue during the intervening period. The Trustee shall mail
notice of each Special Payment and the Special Distribution Date therefor to the
Certificateholder of this Certificate.

     Except as otherwise provided in the Agreement and notwithstanding the
above, the final distribution on this Certificate shall be made after notice
mailed by the Trustee of the pendency of such distribution and only upon
presentation and surrender of this Certificate at the office or agency of the
Trustee specified in such notice.

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

     Reference is hereby made to the further provisions of this Certificate set
forth in the reverse hereof, which further provisions shall for all purposes
have the same effect as if set forth at this place.

     Unless the certificate of authentication hereon has been executed by the
Trustee, by manual signature, this Certificate shall not be entitled to any
benefit under the Agreement or be valid for any purpose or obligatory.

                                      A-4
<PAGE>

          IN WITNESS WHEREOF, the Trustee, on behalf of the Issuer and not in
its individual capacity, has caused this Certificate to be duly executed.

                                            UNITED AIRLINES 2000-1C-2 PASS
                                            THROUGH TRUST

                                            By:  STATE STREET BANK AND TRUST
                                            COMPANY OF CONNECTICUT, NATIONAL
                                            ASSOCIATION, not in its individual
                                            capacity but solely as Trustee

Dated:                                      By:
       ----------------------                   -------------------------------

                                                Name:
                                                      -------------------------

                                                Title:
                                                       ------------------------

                                      A-5
<PAGE>

                    TRUSTEE'S CERTIFICATE OF AUTHENTICATION

     This is one of the Certificates referred to in the within-mentioned Trust
Agreement.

State Street Bank and Trust Company      State Street Bank and Trust
of Connecticut, National Association,    Company of Connecticut, National
not in its individual capacity but       Association, not in its individual
solely as Trustee                        capacity but solely as Trustee

By:                                      By:
    -------------------------                -----------------------------
                                                 Authenticating Agent

                                         By:
                                             -----------------------------

                                      A-6
<PAGE>

                           [REVERSE OF CERTIFICATE]

          The Certificates do not represent a direct obligation of, or an
obligation guaranteed by, or an interest in, the Company or the Trustee or any
of their Affiliates. The Certificates are limited in right or payment, all as
more specifically set forth on the face hereof and in the Agreement. All
payments or distributions made to Certificateholders under the Agreement shall
be made only from the Trust Property and only to the extent that the Trustee
shall have sufficient income or proceeds from the Trust Property to make such
payments in accordance with the terms of the Agreement. Each Certificateholder
of this Certificate, by its acceptance hereof, agrees that it shall look solely
to the income and proceeds from the Trust Property to the extent available for
distribution to such Certificateholder as provided in the Agreement. This
Certificate does not purport to summarize the Agreement and reference is made to
the Agreement for information with respect to the interests, rights, benefits,
obligations, proceeds and duties evidenced hereby. A copy of the Agreement may
be examined during normal business hours at the principal office of the Trustee,
and at such other places, if any, designated by the Trustee, by any
Certificateholder upon request.

          The Agreement permits, with certain exceptions therein provided, the
amendment thereof and the modification of the rights and obligations of the
Company and the rights of the Certificateholders under the Agreement at any time
by the Company and the Trustee with the consent of the Certificateholders
holding Certificates evidencing Fractional Cumulative Interests aggregating not
less than a majority in interest in the Trust. Any such consent by the
Certificateholder of this Certificate shall be conclusive and binding on such
Certificateholder and upon all future Certificateholders of this Certificate and
of any Certificate issued upon the transfer hereof or in exchange hereof or in
lieu hereof whether or not notation of such consent is made upon this
Certificate. The Agreement also permits the amendment thereof, in certain
limited circumstances, without the consent of the Certificateholders of any of
the Certificates.

          As provided in the Agreement and subject to certain limitations
therein set forth, the transfer of this Certificate is registrable in the
Register upon surrender of this Certificate for registration of transfer at the
offices or agencies maintained by the Trustee in its capacity as Registrar, or
by any successor Registrar, at its Corporate Trust Office, duly endorsed or
accompanied by a written instrument of transfer in form satisfactory to the
Trustee and the Registrar duly executed by the Certificateholder hereof or such
Certificateholder's attorney duly authorized in writing, and thereupon one or
more new Certificates of authorized denominations evidencing the same aggregate
Fractional Undivided Interest in the Trust shall be issued to the designated
transferee or transferees.

          The Certificates are issuable only as registered Certificates without
coupons in minimum denominations of $1,000 Fractional Undivided Interest and
integral multiples of $1,000 in excess thereof. As provided in the Agreement and
subject to certain limitations therein set forth, the Certificates are
exchangeable for new Certificates of authorized denominations evidencing the

                                      A-7
<PAGE>

same aggregate Fractional Undivided Interest in the Trust, as requested by the
Certificateholder surrendering the same.

          No service charge shall be made for any such registration of transfer
or exchange, but the Trustee shall require payment by the Certificateholder of a
sum sufficient to cover any tax or governmental charge payable in connection
therewith.

          The Trustee, the Registrar, and any agent of the Trustee or the
Registrar may treat the person in whose name this Certificate is registered as
the owner hereof for all purposes, and neither the Trustee, the Registrar, nor
any such agent shall be affected by any notice to the contrary.

          The obligations and responsibilities created by the Agreement and the
Trust created thereby shall terminate upon the distribution to
Certificateholders of all amounts required to be distributed to them pursuant to
the Agreement and the disposition of all property held as part of the Trust
Property.

                                      A-8
<PAGE>

                            FORM OF TRANSFER NOTICE

          FOR VALUE RECEIVED the undersigned registered holder hereby sell(s),
assign(s) and transfer(s) unto

Insert Taxpayer Identification No.

-------------------------------------------------------------------------------
please print or typewrite name and address including zip code of assignee

-------------------------------------------------------------------------------
the within Certificate and all rights thereunder, hereby irrevocably
constituting and appointing

-------------------------------------------------------------------------------
attorney to transfer said Certificate on the books of the Trustee with full
power of substitution in the premises.

Date:                                       [Name of Transferor]

                                            -----------------------------------

                                       NOTE:  The signature must correspond with
                                       the name as written upon the face of the
                                       within-mentioned instrument in every
                                       particular, without alteration or any
                                       change whatsoever.

Signature Guarantee:
                     ------------------

                                      A-9
<PAGE>

                               MANNER OF TRANSFER

     This form shall be completed if this Certificate or an interest herein is
transferred within two years after the later of the original issuance of the
certificate or the last date on which this certificate was held by United Air
Lines, Inc., the Trustee or any Affiliate of any such Person.  This form shall
be delivered to the Trustee upon completion.

     The Holder of the United Airlines Enhanced Pass Through Certificate, Series
2000-1C-2 hereby transfers a beneficial interest in the aforesaid certificate to
________________, in one of the following permissible transfers:

     [_]  To United Air Lines, Inc.

     [_]  To a qualified institutional buyer in compliance with Rule 144A under
          the Securities Act

     [_]  To an institutional accredited investor acquiring $100,000 or more
          aggregate principal amount of this Certificate that has, prior to this
          transfer, furnished to the Trustee a signed letter containing certain
          representations and agreements relating to the restrictions on
          transfer of this Certificate

     [_]  Pursuant to the exemption from registration provided by Rule 144 under
          the Securities Act (if available)

     [_]  Pursuant to an effective registration statement under the Securities
          Act

                                     A-10
<PAGE>

                                   EXHIBIT B
                                   ---------

                        SCHEDULED PAYMENTS OF PRINCIPAL
                           ON CLASS C-2 CERTIFICATES

      Payment Date            Principal Payment
      ------------            -----------------

                                      B-1
<PAGE>

                                   EXHIBIT C
                                   ---------

                               TRUST OWNED NOTES
                        PRINCIPAL AMOUNTS AND MATURITIES

  Trust Owned Notes                  Principal Amount                 Maturity
  -----------------                  ----------------                 --------

                                      C-1
<PAGE>

                                   EXHIBIT D

                 AIRCRAFT, REGISTRATION NUMBERS AND MATURITIES

<TABLE>
<CAPTION>
                                         Aircraft
                                       Registration
  Aircraft                                Number                       Maturity
  --------                             ------------                    --------
<S>                                    <C>                            <C>

</TABLE>

                                      D-1
<PAGE>

                                   EXHIBIT E

                                NOTE DOCUMENTS
<TABLE>
<CAPTION>
                       Aircraft
                     Registration
Aircraft                Number                  Note Document
--------             ------------              --------------
<S>                  <C>              <C>
Owned
-----
Airbus A320-232         N454UA        Participation Agreement
                                      Trust Indenture and Mortgage
                                      Equipment Note, Series A-1
                                      United Equipment Note, Series A-2
                                      United Equipment Note, Series B

Airbus A320-232         N455UA        Participation Agreement
                                      Trust Indenture and Mortgage
                                      United Equipment Note, Series A-1
                                      United Equipment Note, Series A-2
                                      United Equipment Note, Series B

Airbus A320-232         N456UA        Participation Agreement
                                      Trust Indenture and Mortgage
                                      United Equipment Note, Series A-1
                                      United Equipment Note, Series A-2
                                      United Equipment Note, Series B

Airbus A320-232         N457UA        Participation Agreement
                                      Trust Indenture and Mortgage
                                      United Equipment Note, Series A-1
                                      United Equipment Note, Series A-2
                                      United Equipment Note, Series B

Airbus A320-232         N458UA        Participation Agreement
                                      Trust Indenture and Mortgage
                                      United Equipment Note, Series A-1
                                      United Equipment Note, Series A-2
                                      United Equipment Note, Series B

Airbus A320-232         N459UA        Participation Agreement
                                      Trust Indenture and Mortgage
                                      United Equipment Note, Series A-1
                                      United Equipment Note, Series A-2
                                      United Equipment Note, Series B
</TABLE>

                                      E-1
<PAGE>

<TABLE>
<CAPTION>
                       Aircraft
                     Registration
Aircraft                Number                  Note Document
--------             ------------              --------------
<S>                  <C>              <C>
Boeing 757-222          N596UA        Participation Agreement
                                      Trust Indenture and Mortgage
                                      United Equipment Note, Series A-1
                                      United Equipment Note, Series A-2
                                      United Equipment Note, Series B

Boeing 767-322ER        N673UA        Participation Agreement
                                      Trust Indenture and Mortgage
                                      United Equipment Note, Series A-1
                                      United Equipment Note, Series A-2
                                      United Equipment Note, Series B

Boeing 767-322ER        N674UA        Participation Agreement
                                      Trust Indenture and Mortgage
                                      United Equipment Note, Series A-1
                                      United Equipment Note, Series A-2
                                      United Equipment Note, Series B

Boeing 777-222ER        N207UA        Participation Agreement
                                      Trust Indenture and Mortgage
                                      United Equipment Note, Series A-1
                                      United Equipment Note, Series A-2
                                      United Equipment Note, Series B

Boeing 777-222ER        N208UA        Participation Agreement
                                      Trust Indenture and Mortgage
                                      United Equipment Note, Series A-1
                                      United Equipment Note, Series A-2
                                      United Equipment Note, Series B

Boeing 777-222ER        N209UA        Participation Agreement
                                      Trust Indenture and Mortgage
                                      United Equipment Note, Series A-1
                                      United Equipment Note, Series A-2
                                      United Equipment Note, Series B

Boeing 777-222ER        N210UA        Participation Agreement
</TABLE>

                                      E-2
<PAGE>
<TABLE>
<CAPTION>
                                    Trust Indenture and Mortgage
                                    United Equipment Note, Series A-1
                                    United Equipment Note, Series A-2
                                    United Equipment Note, Series B

                     Aircraft
Aircraft           Registration
Leased                Number                      Note Document
------             ------------                   --------------
<S>                <C>              <C>
Boeing 747-422        N171UA        Participation Agreement, as amended
                                    First Amended and Restated Trust Indenture
                                     and Security Agreement
                                    Lease Agreement, as amended
                                    747 Lease Equipment Note, Series A-1
                                    747 Lease Equipment Note, Series B
                                    747 Lease Equipment Note, Series C-2
</TABLE>

                                      E-3

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