Document:

<PAGE>

                                                                    Exhibit 4.28

                              CLASS B CERTIFICATE

REGISTERED                                                          $200,309,000
                                                   Fractional Undivided Interest

No.  R - 1
                                                            CUSIP NO.  909317AT6

     UNLESS THIS CERTIFICATE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF THE
     DEPOSITORY TRUST COMPANY, A NEW YORK CORPORATION ("DTC"), TO THE TRUSTEE OR
     ITS AGENT FOR REGISTRATION OF TRANSFER, EXCHANGE OR PAYMENT, AND ANY
     CERTIFICATE ISSUED IN EXCHANGE FOR THIS CERTIFICATE IS REGISTERED IN THE
     NAME OF CEDE & CO. OR IN SUCH OTHER NAME AS IS REQUESTED BY AN AUTHORIZED
     REPRESENTATIVE OF DTC (AND ANY PAYMENT HEREON IS MADE TO CEDE & CO. OR TO
     SUCH OTHER ENTITY AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC),
     ANY TRANSFER, PLEDGE OR OTHER USE HEREOF FOR VALUE OR OTHERWISE BY OR TO
     ANY PERSON IS WRONGFUL INASMUCH AS THE REGISTERED OWNER HEREOF, CEDE & CO.,
     HAS AN INTEREST HEREIN.

     TRANSFERS OF THIS CERTIFICATE SHALL BE LIMITED TO TRANSFERS IN WHOLE, BUT
     NOT IN PART, TO NOMINEES OF DTC OR TO A SUCCESSOR THEREOF OR SUCH
     SUCCESSOR'S NOMINEE AND TRANSFERS OF PORTIONS OF THIS CERTIFICATE SHALL BE
     LIMITED TO TRANSFERS MADE IN ACCORDANCE WITH THE RESTRICTIONS SET FORTH IN
     SECTIONS 3.05 AND 3.06 OF THE PASS THROUGH TRUST AGREEMENT REFERRED TO
     HEREIN.

     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.
<PAGE>

         UNITED AIRLINES 2000-1B ENHANCED ENHANCED PASS THROUGH TRUST

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

            Final Expected Regular Distribution Date: July 1, 2011

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. and a promissory note issued by AFE Trust ("AFE
Note").

          THIS CERTIFIES THAT CEDE & CO., for value received, is the registered
owner of a TWO HUNDRED MILLION, THREE HUNDRED NINE THOUSAND DOLLARS
($200,309,000) Fractional Undivided Interest in the United Airlines 2000-1B 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. 2000-1B (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 2000-1B" (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 Note Purchase Agreements.  The
property of the Trust includes  (i) certain Equipment Notes, 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, (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 Note Purchase Agreements and (iv) all monies receivable by the
Subordination Agent under the Liquidity Facilities for the Trust (the "Trust
                                                                       -----
Property"). Each issue of the Trust Owned Notes is secured directly or
--------
indirectly by, among other things, a security interest 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 8.030%.

          Subject to and in accordance with the terms of the Agreement, the
Intercreditor Agreement and the Note Purchase Agreements, from and to the extent
of funds then available to the
<PAGE>

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 Note Purchase
Agreements, 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 or obligatory for any purpose.
<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 2000-1B 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:________________________________
<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 Connecticut, National Association,      of Connecticut, National Association,
not in its individual capacity but solely  not in its individual capacity but
as Trustee                                 solely as Trustee

By:______________________                  By:___________________________
                                                Authenticating Agent

                                           By:___________________________
<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
same aggregate Fractional Undivided Interest in the Trust, as requested by the
Certificateholder surrendering the same.
<PAGE>

          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.
<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:________________<PAGE>

                                                                          EX4.29

                             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 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
<PAGE>

     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.
<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%.

          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
<PAGE>

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.
<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:
                                                 ----------------------------
<PAGE>

                    TRUSTEE'S CERTIFICATE OF AUTHENTICATION

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

<TABLE>
<CAPTION>

<S>                                           <C>
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 solely     not in its individual capacity but solely
as Trustee                                    as Trustee

By:______________________                     By:___________________________
                                                    Authenticating Agent

                                              By:___________________________

</TABLE>

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

          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.

<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:
<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

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00013-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00013-of-00352.parquet"}]]