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                                                                    EXHIBIT 4.18

                              CLASS A-2 CERTIFICATE

                             REGISTERED $332,770,000
                          Fractional Undivided Interest
                                    No. R - 1
No. 2                         CUSIP NO. 909317 AV 1

         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.




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              UNITED AIRLINES 2000-2A-2 ENHANCED PASS THROUGH TRUST

                      UNITED AIRLINES ENHANCED PASS THROUGH
                          CERTIFICATE, SERIES 2000-2A-2

             Final Expected Regular Distribution Date: April 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 United Air
Lines, Inc.

         THIS CERTIFIES THAT CEDE & CO., for value received, is the registered
owner of a THREE HUNDRED THIRTY-TWO MILLION SEVEN HUNDRED SEVENTY THOUSAND
DOLLAR ($332,770,000) Fractional Undivided Interest in the United Airlines
2000-2A-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 December 14, 2000 (the
"Basic Agreement"), as supplemented by Trust Supplement No. 2000-2A-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
2000-2A-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 Note Purchase Agreement. The
property of the Trust includes (i) certain 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, (iii) all rights of such Trust and the
Trustee, on behalf of such Trust, under the Intercreditor Agreement and the 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 Note Purchase Agreement and (iv) all monies
receivable by the Subordination Agent under the Liquidity Facility for the Trust
(the "Trust Property"). Each issue of the Notes is secured directly or
indirectly by, among other things, a security interest in the Aircraft owned by
the Company.

         The Certificates represent Fractional Undivided Interests in the Trust
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 7.186%.

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



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the Trustee, there shall be distributed on each April 1 and October 1 (a
"Regular Distribution Date"), commencing on April 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 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
Agreement, if Special Payments on the 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
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.



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         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 2000-2A-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: December 14, 2000                   By: /s/ John G. Correia
                                              ---------------------------------
                                               Name:  John G. Correia
                                               Title: Assistant Vice President




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                     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 of    State Street Bank and Trust Company 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: /s/ John G. Correia                           By: /s/ John G. Correia
                                                          Authenticating Agent

                                                  By: John G. Correia




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                            [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.




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         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.