EX-4.1


 Exhibit 4.1 

EXECUTION VERSION 
  

 
  

TRUST SUPPLEMENT No. 2018-1B-O 

Dated as of May 23, 2018 

between 
 WILMINGTON TRUST,
NATIONAL ASSOCIATION 
 as Trustee, 

and 
 UNITED AIRLINES, INC. 

to 
 PASS THROUGH TRUST AGREEMENT

 Dated as of October 3, 2012 

$225,729,000 
 United Airlines
Pass Through Trust 2018-1B-O 
 4.600% United Airlines Pass
Through Certificates, Series 2018-1B-O 
  

 
  






 TABLE OF CONTENTS 
  

					
	 	  	Page	 
	 ARTICLE I THE CERTIFICATES
	  	 	3	 
	 Section 1.01. The Certificates
	  	 	3	 
		
	 ARTICLE II DEFINITIONS
	  	 	5	 
	 Section 2.01. Definitions
	  	 	5	 
		
	 ARTICLE III DISTRIBUTIONS; STATEMENTS TO CERTIFICATEHOLDERS
	  	 	12	 
	 Section 3.01. Statements to Applicable Certificateholders
	  	 	12	 
	 Section 3.02. Special Payments Account
	  	 	14	 
	 Section 3.03. Distributions from Special Payments Account
	  	 	14	 
	 Section 3.04. Limitation of Liability for Payments
	  	 	15	 
		
	 ARTICLE IV DEFAULT
	  	 	15	 
	 Section 4.01. Purchase Rights of Certificateholders
	  	 	15	 
	 Section 4.02. Amendment of Section 6.05 of the Basic Agreement
	  	 	18	 
		
	 ARTICLE V THE TRUSTEE
	  	 	18	 
	 Section 5.01. Delivery of Documents; Delivery Dates
	  	 	18	 
	 Section 5.02. Withdrawal of Deposits
	  	 	20	 
	 Section 5.03. The Trustee
	  	 	20	 
	 Section 5.04. Representations and Warranties of the Trustee
	  	 	20	 
	 Section 5.05. Trustee Liens
	  	 	21	 
		
	 ARTICLE VI ADDITIONAL AMENDMENT; SUPPLEMENTAL AGREEMENTS
	  	 	21	 
	 Section 6.01. Amendment of Section 5.02 of the Basic Agreement
	  	 	21	 
	 Section 6.02. Supplemental Agreements Without Consent of Applicable
Certificateholders
	  	 	21	 
	 Section 6.03. Supplemental Agreements with Consent of Applicable Certificateholders
	  	 	22	 
	 Section 6.04. Consent of Holders of Certificates Issued under Other Trusts
	  	 	22	 
		
	 ARTICLE VII TERMINATION OF TRUST
	  	 	23	 
	 Section 7.01. Termination of the Applicable Trust
	  	 	23	 
		
	 ARTICLE VIII MISCELLANEOUS PROVISIONS
	  	 	25	 
	 Section 8.01. Basic Agreement Ratified
	  	 	25	 
	 Section 8.02. GOVERNING LAW
	  	 	25	 
	 Section 8.03. Execution in Counterparts
	  	 	25	 
	 Section 8.04. Intention of Parties
	  	 	25	 

  

					
	Exhibit A	  	-	  	Form of Certificate
	Exhibit B	  	-	  	DTC Letter of Representations
	Exhibit C	  	-	  	Form of Assignment and Assumption Agreement

  






 This Trust Supplement No.
2018-1B-O, dated as of May 23, 2018 (herein called the “Trust Supplement”), between United Airlines, Inc., a Delaware corporation (the
“Company”), and Wilmington Trust, National Association (the “Trustee”), to the Pass Through Trust Agreement, dated as of October 3, 2012, between the Company (formerly known as Continental Airlines, Inc.) and
the Trustee (the “Basic Agreement”). 
 W I T N E S S E T
H: 
 WHEREAS, the Basic Agreement, unlimited as to the aggregate face amount of Certificates (unless otherwise specified herein,
capitalized terms used herein without definition having the respective meanings specified in the Basic Agreement) which may be issued thereunder, has heretofore been executed and delivered; 

WHEREAS, the Company is the owner of or has obtained commitments from Boeing for the delivery of two Boeing
737-800 aircraft, six Boeing 737 MAX 9 aircraft, five Boeing 787-9 aircraft and three Boeing 777-300ER aircraft (collectively,
the “Applicable Aircraft”); 
 WHEREAS, the Company has financed or intends to finance each of the Applicable Aircraft;

 WHEREAS, the Company entered into the Original NPA (as defined below) to provide, with respect to each of the Applicable Aircraft, for
the issuance, pursuant to an Indenture, of Series AA Equipment Notes and Series A Equipment Notes (each as defined in the NPA) to finance a portion of the purchase price of such Applicable Aircraft; 

WHEREAS, concurrently herewith the Company is entering into the NPA Amendment (as defined below) amending the Original NPA to provide, with
respect to each Applicable Aircraft, for the issuance, pursuant to the applicable Indenture, on a recourse basis, of Series B Equipment Notes to finance a portion of the purchase price of such Applicable Aircraft; 

WHEREAS, in the case of each Financed Aircraft, the Company has issued pursuant to an Indenture, on a recourse basis, Series AA Equipment
Notes and Series A Equipment Notes, and will issue on the Class B Issuance Date pursuant to such Indenture (as amended by the applicable Indenture Amendment), on a recourse basis, Series B Equipment Notes; 

WHEREAS, in the case of each Remaining Aircraft, the Company will issue pursuant to an Indenture, on a recourse basis, Series AA Equipment
Notes, Series A Equipment Notes and Series B Equipment Notes to finance a portion of the purchase price of such Remaining Aircraft; 

WHEREAS, the Trustee hereby declares the creation of the United Airlines Pass Through Trust 2018-1B-O (the “Applicable Trust”) for the benefit of the Applicable Certificateholders, and the initial Applicable Certificateholders as the grantors of the Applicable Trust, by their
respective acceptances of the Applicable Certificates (as defined below), join in the creation of the Applicable Trust with the Trustee; 

  
 
 1
 







 WHEREAS, all Certificates to be issued by the Applicable Trust will evidence Fractional Undivided
Interests in the Applicable Trust and will convey no rights, benefits or interests in respect of any property other than the Trust Property except for those Certificates to which an Escrow Receipt has been affixed; 

WHEREAS, the Escrow Agent and the Underwriters have contemporaneously herewith entered into an Escrow Agreement with the Escrow Paying Agent
pursuant to which the Underwriters have delivered to the Escrow Agent the proceeds from the sale of the Applicable Certificates (to the extent not used to purchase Series B Equipment Notes on the Series B Issuance Date), and have irrevocably
instructed the Escrow Agent to withdraw and pay funds from such proceeds upon request and proper certification by the Trustee to purchase Series B Equipment Notes in respect of the Remaining Aircraft as the conditions set forth in the NPA for such
purchase are satisfied from time to time prior to the Delivery Period Termination Date; 
 WHEREAS, the Escrow Agent on behalf of the
Applicable Certificateholders has contemporaneously herewith entered into a Deposit Agreement with the Depositary under which the Deposits referred to therein will be made and from which it will withdraw funds to allow the Trustee to purchase Series
B Equipment Notes in respect of the Remaining Aircraft from time to time prior to the Delivery Period Termination Date; 
 WHEREAS, pursuant
to the terms and conditions of the Basic Agreement as supplemented by this Trust Supplement (the “Agreement”) and the NPA, on the Class B Issuance Date (with respect to each Financed Aircraft) and thereafter (upon the financing
of a Remaining Aircraft under the NPA), the Trustee on behalf of the Applicable Trust, using a portion of the proceeds of the sale of the Applicable Certificates (in the case of Financed Aircraft) or using funds withdrawn under the Escrow Agreement
(in the case of Remaining Aircraft), shall purchase one or more Series B Equipment Notes having the same interest rate as, and final maturity date not later than the final Regular Distribution Date of, the Applicable Certificates issued hereunder
and shall hold such Series B Equipment Notes in trust for the benefit of the Applicable Certificateholders; 
 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; and 

WHEREAS, this Trust Supplement is subject to the provisions of the Trust Indenture Act of 1939, as amended, and shall, to the extent
applicable, be governed by such provisions. 
 NOW THEREFORE, in consideration of the premises herein, it is agreed between the Company and
the Trustee as follows: 

  
 2 







 ARTICLE I 

THE CERTIFICATES 

Section 1.01. The Certificates. There is hereby created a series of Certificates to be issued under the Agreement to be
distinguished and known as “United Airlines Pass Through Certificates, Series 2018-1B-O” (hereinafter defined as the “Applicable
Certificates”). Each Applicable Certificate represents a Fractional Undivided Interest in the Applicable Trust created hereby. The Applicable Certificates shall be the only instruments evidencing a Fractional Undivided Interest in the
Applicable Trust. 
 The terms and conditions applicable to the Applicable Certificates are as follows: 

(a) The aggregate face amount of the Applicable Certificates that shall be authenticated under the Agreement (except for
Applicable Certificates authenticated and delivered under Sections 3.03, 3.04, 3.05 and 3.06 of the Basic Agreement) is $225,729,000. 

(b) The Regular Distribution Dates with respect to any distribution of Scheduled Payments means March 1 and
September 1 of each year, commencing on September 1, 2018, until distribution of all of the Scheduled Payments to be made under the Series B Equipment Notes has been made. 

(c) The Special Distribution Dates with respect to the Applicable Certificates means any Business Day on which a Special
Payment is to be distributed pursuant to the Agreement. 
 (d) At the Escrow Agent’s request under the Escrow Agreement,
the Trustee shall affix the corresponding Escrow Receipt to each Applicable Certificate. In any event, any transfer or exchange of any Applicable Certificate shall also effect a transfer or exchange of the related Escrow Receipt. Prior to the Final
Distribution, no transfer or exchange of any Applicable Certificate shall be permitted unless the corresponding Escrow Receipt is attached thereto and also is so transferred or exchanged. By acceptance of any Applicable Certificate to which an
Escrow Receipt is attached, each Holder of such an Applicable Certificate acknowledges and accepts the restrictions on transfer of the Escrow Receipt set forth herein and in the Escrow Agreement. 

(e) (i) The Applicable Certificates shall be in the form attached hereto as Exhibit A. Any Person acquiring or accepting
an Applicable Certificate or an interest therein will, by such acquisition or acceptance, be deemed to have represented and warranted to and for the benefit of the Company that either (A) no assets of an employee benefit plan subject to Title I
of the Employee Retirement Income Security Act of 1974, as amended (“ERISA”), a plan subject to Section 4975 of the Internal Revenue Code of 1986, as amended (the “Code”), or a governmental, church or foreign
plan subject to a law that is similar to Title I of ERISA or Section 4975 of the Code (a “Similar Law Plan”) have been used to purchase or hold such Applicable Certificate or an interest therein or (B) the purchase and
holding of such Applicable Certificate or an interest therein either (x) in the case of assets of an employee benefit plan subject to Title I of 

  
 3 







 
ERISA or a plan subject to Section 4975 of the Code, are exempt from the prohibited transaction restrictions of ERISA and the Code pursuant to one or more prohibited transaction statutory or
administrative exemptions or (y) in the case of assets of a Similar Law Plan, will not violate any similar state, local or foreign law. 

(ii) The Applicable Certificates shall be Book-Entry Certificates and shall be subject to the conditions set forth in the
Letter of Representations between the Applicable Trust and the Clearing Agency attached hereto as Exhibit B. 
 (f) Any
Person who is an employee benefit plan subject to Title I of ERISA, a plan subject to Section 4975 of the Code, or an entity whose underlying assets are deemed to include “plan assets” by reason of such a plan’s investment in
such entity (a “Benefit Plan Investor”) and is acquiring or accepting an Applicable Certificate or an interest therein will, by such acquisition or acceptance, be deemed to have represented and warranted to and for the benefit of
the Company, the Underwriters and their respective affiliates that (i) the decision to acquire or accept the Applicable Certificate or interest therein has been made by a duly authorized fiduciary of the Benefit Plan Investor that (A) is
independent (as that term is used in 29 C.F.R. 2510.3-21(c)(1)) of the Company, each of the Underwriters, and their respective affiliates; (B) is a bank, an insurance carrier, a registered investment
adviser, a registered broker-dealer, or an independent fiduciary that holds, or has under management or    control, total assets of at least $50 million (in each case, as specified in 29 C.F.R.
2510.3-21(c)(1)(i)(A)-(E)); (C) is capable of evaluating investment risks independently, both in general and with regard to particular transactions and investment strategies (including, without limitation,
with respect to the decision to acquire or accept the Applicable Certificate or interest therein); (D) has been fairly informed that the Company, the Underwriters, and their respective affiliates have not and will not undertake to provide impartial
investment advice, or to give advice in a fiduciary capacity, in connection with the acquisition or acceptance of the Applicable Certificate or interest therein; (E) has been fairly informed of the existence and nature of the financial
interests that the Company, the Underwriters, and their respective affiliates have in the Benefit Plan Investor’s acquisition or acceptance of the Applicable Certificate or interest therein, which interests may conflict with the interest of the
Benefit Plan Investor, as more fully described in the offering materials; and (F) is a fiduciary under ERISA or the Code, or both, with respect to the decision to acquire or accept the Applicable Certificate or interest therein and is
responsible for exercising (and has exercised) independent judgment in evaluating whether to invest the assets of such Benefit Plan Investor in the Applicable Certificate or interest therein; and (ii) neither the Benefit Plan Investor nor such
duly authorized fiduciary of the Benefit Plan Investor is paying the Company, any Underwriter, or any of their respective affiliates, any fee or other compensation directly for the provision of investment advice (as opposed to other services) in
connection with the Benefit Plan Investor’s acquisition or acceptance of the Applicable Certificate or interest therein. 

(g) The “Participation Agreements” as defined in this Trust Supplement are the “Note Purchase Agreements”
referred to in the Basic Agreement. 

  
 4 







 (h) The Applicable Certificates are subject to the Intercreditor Agreement, the
Deposit Agreement and the Escrow Agreement. 
 (i) The Applicable Certificates are entitled to the benefits of the Liquidity
Facility. 
 (j) The Responsible Party is the Company. 

(k) The date referred to in clause (i) of the definition of the term “PTC Event of Default” in the Basic
Agreement is the Final Maturity Date. 
 (l) The “particular sections of the Note Purchase Agreement”, for purposes
of clause (3) of Section 7.07 of the Basic Agreement, are Section 8.1 of each Participation Agreement. 
 (n)
The Series B Equipment Notes to be acquired and held in the Applicable Trust, and the related Aircraft and Note Documents, are described in the NPA. 

ARTICLE II 
 DEFINITIONS 

Section 2.01. Definitions. For all purposes of the Basic Agreement as supplemented by this Trust Supplement, the following
capitalized terms have the following meanings (any term used herein which is defined in both this Trust Supplement and the Basic Agreement shall have the meaning assigned thereto in this Trust Supplement for purposes of the Basic Agreement as
supplemented by this Trust Supplement):  
 Agreement: Has the
meaning specified in the recitals hereto. 
 Aircraft: Means each of the Applicable Aircraft (or Substitute Aircraft)
in respect of which a Participation Agreement is to be or has been, as the case may be, entered into in accordance with the NPA (or any Substitute Aircraft, including engines therefor, owned by the Company and securing one or more Series B Equipment
Notes). 
 Aircraft Purchase Agreement: Has the meaning specified in the NPA. 

Applicable Aircraft: Has the meaning specified in the recitals hereto. 

Applicable Certificate: Has the meaning specified in Section 1.01 of this Trust Supplement. 

Applicable Certificateholder: Means the Person in whose name an Applicable Certificate is registered on the Register for
the Applicable Certificates. 
 Applicable Closing Date: Has the meaning specified in Section 5.01(b) of this
Trust Supplement. 

  
 5 







 Applicable Participation Agreement: Has the meaning specified in
Section 5.01(b) of this Trust Supplement. 
 Applicable Trust: Has the meaning specified in the recitals hereto.

 Assignment and Assumption Agreement: Means the assignment and assumption agreement substantially in the form of
Exhibit C hereto executed and delivered in accordance with Section 7.01 of this Trust Supplement. 
 Basic
Agreement: Has the meaning specified in the first paragraph of this Trust Supplement. 
 Boeing: Means The Boeing
Company. 
 Business Day: Means any day other than a Saturday, a Sunday or a day on which commercial banks are
required or authorized to close in New York, New York, Chicago, Illinois, or, so long as any Applicable Certificate is Outstanding, the city and state in which the Trustee, the Subordination Agent or any Loan Trustee maintains its Corporate Trust
Office or receives and disburses funds. 
 Certificate: Has the meaning specified in the Intercreditor Agreement. 

Certificate Buyout Event: Means that a United Bankruptcy Event has occurred and is continuing and either of the
following events has occurred: (A) both (i) the 60-day period specified in Section 1110(a)(2)(A) of the U.S. Bankruptcy Code (the “60-Day
Period”) has expired and (ii) the Company has not entered into one or more agreements under Section 1110(a)(2)(A) of the U.S. Bankruptcy Code to perform all of its obligations under all of the Indentures or, if it has entered into
such agreements, has at any time thereafter failed to cure any default under any of the Indentures in accordance with Section 1110(a)(2)(B) of the U.S. Bankruptcy Code; or (B) prior to the expiry of the
60-Day Period, the Company shall have abandoned any Aircraft. 
 Class: Has
the meaning specified in the Intercreditor Agreement. 
 Class B Issuance Date: Has the meaning
specified in the NPA. 
 Closing Notice: Has the meaning specified in the NPA. 

Company: Has the meaning specified in the first paragraph of this Trust Supplement. 

Controlling Party: Has the meaning specified in the Intercreditor Agreement. 

Cut-off Date: Means the earlier of (a) the Delivery Period Termination Date
and (b) the date on which a Triggering Event occurs. 

  
 6 







 Delivery Period Termination Date: Means the earlier of
(a) August 31, 2018 (provided that, if a labor strike occurs or continues at Boeing after February 14, 2018 and on or prior to such date referred to in this clause (a), such date shall be extended by adding thereto the number of days
that such strike continued in effect after February 14, 2018, but not more than 60 days (such extended number of days, the “Strike Period”)), and (b) the date on which Series B Equipment Notes issued with respect to all of
the Applicable Aircraft (including any Substitute Aircraft in lieu of any Applicable Aircraft) have been purchased by the Applicable Trust and the United Airlines Pass Through Trust
2018-1B-O in accordance with the NPA. 

Deposit Agreement: Means the Deposit Agreement dated as of May 23, 2018 relating to the Applicable Certificates
between the Depositary and the Escrow Agent, as the same may be amended, supplemented or otherwise modified from time to time in accordance with its terms. 

Depositary: Means Citibank, N.A.  

Deposits: Has the meaning specified in the Deposit Agreement. 

Distribution Date: Means any Regular Distribution Date or Special Distribution Date as the context requires. 

ERISA: Has the meaning specified in Section 1.01(e) of this Trust Supplement. 

Escrow Agent: Means, initially, U.S. Bank National Association and any replacement or successor therefor appointed in
accordance with the Escrow Agreement. 
 Escrow Agreement: Means the Escrow and Paying Agent Agreement dated as of
May 23, 2018 relating to the Applicable Certificates, among the Escrow Agent, the Escrow Paying Agent, the Trustee and the Underwriters, as the same may be amended, supplemented or otherwise modified from time to time in accordance with its
terms. 
 Escrow Paying Agent: Means the Person acting as paying agent under the Escrow Agreement. 

Escrow Receipt: Means the receipt substantially in the form annexed to the Escrow Agreement representing a fractional
undivided interest in the funds held in escrow thereunder. 
 Final Distribution: Has the meaning specified in the
Escrow Agreement. 
 Final Maturity Date: Means September 1, 2027. 

Final Withdrawal: Has the meaning specified in the Escrow Agreement. 

  
 7 







 Final Withdrawal Date: Has the meaning specified in the Escrow Agreement.

 Final Withdrawal Notice: Has the meaning specified in Section 5.02 of this Trust Supplement. 

Financed Aircraft: Means each Applicable Aircraft (or Substitute Aircraft) in respect of which Series AA Equipment
Notes and Series A Equipment Notes have been issued on or prior to the Class B Issuance Date. 
 Indenture:
Means each of the separate trust indentures and mortgages relating to the Aircraft, each as specified or described in a Closing Notice having been or to be, as applicable, delivered pursuant to the NPA or the related Participation Agreement, in each
case as the same may be further amended, supplemented or otherwise modified from time to time in accordance with its terms (including, as to each Indenture with respect to a Financed Aircraft, as amended pursuant to the applicable Indenture
Amendment). 
 Indenture Amendment: Means, with respect to an Indenture relating to a Financed Aircraft, the first
amendment thereto, dated as of the date hereof, between the Company and the Loan Trustee. 
 Intercreditor Agreement:
Means the amended and restated intercreditor agreement dated as of the date hereof among the Trustee, the Other Trustees party thereto, the Liquidity Provider, the liquidity provider relating to the Class AA Certificates and the Class A
Certificates and Wilmington Trust, National Association, as Subordination Agent and as trustee thereunder, as may be further amended, supplemented or otherwise modified from time to time in accordance with its terms. 

Investors: Means the Underwriters, together with all subsequent beneficial owners of the Applicable Certificates. 

Liquidity Facility: Means, initially, the Revolving Credit Agreement dated as of the date hereof relating to the
Applicable Certificates, between the Liquidity Provider and Wilmington Trust, National Association, as Subordination Agent, as agent and trustee for the Applicable Trust, and, from and after the replacement of such agreement pursuant to the
Intercreditor Agreement, the replacement liquidity facility therefor, in each case as amended, supplemented or otherwise modified from time to time in accordance with their respective terms. 

Liquidity Provider: Means, with respect to the Applicable Certificates, initially, National Australia Bank Limited,
acting through its New York Branch, and any replacements or successors therefor appointed in accordance with the Intercreditor Agreement. 

Make-Whole Amount: Has the meaning specified in any Indenture. 

  
 8 







 Note Documents: Means the Series B Equipment Notes with respect to the
Applicable Certificates and, with respect to any such Series B Equipment Note, the Indenture and the Participation Agreement relating to such Series B Equipment Note. 

Notice of Purchase Withdrawal: Has the meaning specified in the Deposit Agreement. 

NPA: Means the Original NPA, as amended by the NPA Amendment, providing for, among other things, the purchase of Series
B Equipment Notes by the Trustee on behalf of the Applicable Trust, as the same may be further amended, supplemented or otherwise modified from time to time, in accordance with its terms. 

NPA Amendment: Means Amendment No. 1 to the Original NPA, dated as of the date hereof, among the Company, the Other
Trustees, the Trustee, the Subordination Agent, the Escrow Agent, the Escrow Paying Agent and the escrow agent and paying agent relating the Class AA Certificates and the Class A Certificates. 

Original NPA: Means the Note Purchase Agreement, dated as of February 14, 2018, among the Company, the Other
Trustees, the Subordination Agent, and the escrow agent and the paying agent relating the Class AA Certificates and the Class A Certificates. 

Other Agreements: Means (i) the Basic Agreement, as supplemented by Trust Supplement No. 2018-1AA-O dated as of February 14, 2018 relating to United Airlines Pass Through Trust
2018-1AA-O, (ii) the Basic Agreement, as supplemented by Trust Supplement No.
2018-1A-O dated as of February 14, 2018 relating to United Airlines Pass Through Trust
2018-1A-O, (iii) the Basic Agreement, as supplemented by a Trust Supplement relating to any Additional Trust and (iv) the Basic Agreement, as supplemented by a
Trust Supplement relating to any Refinancing Trust. 
 Other Trustees: Means the trustees under the Other Agreements,
and any successor or other trustee appointed as provided therein. 
 Other Trusts: Means the United Airlines Pass
Through Trust 2018-1AA-O, the United Airlines Pass Through Trust 2018-1A-O, an Additional
Trust or Trusts, if any, and a Refinancing Trust or Trusts, if any, created by the Other Agreements. 
 Participation
Agreement: Means each Participation Agreement having been or to be, as applicable, entered into by the Trustee and the Other Trustees pursuant to the NPA, as the same may be amended, supplemented or otherwise modified in accordance with its
terms (including, as to each Participation Agreement with respect to a Financed Aircraft, as amended pursuant to the applicable Participation Agreement Amendment). 

Participation Agreement Amendment: Means, with respect to each Participation Agreement relating to a Financed Aircraft,
the first amendment thereto, dated as of the date hereof, among the initial parties to such Participation Agreement and the Trustee. 

  
 9 







 Pool Balance: Means, as of any date, (i) the original aggregate face
amount of the Applicable Certificates less (ii) the aggregate amount of all payments made as of such date in respect of such Applicable Certificates or in respect of Deposits other than payments made in respect of interest or premium (including
Make-Whole Amount) thereon or reimbursement of any costs or expenses incurred in connection therewith. The Pool Balance as of any date shall be computed after giving effect to any special distribution with respect to unused Deposits, payment of
principal of the Series B Equipment Notes or payment with respect to other Trust Property and the distribution thereof to be made on that date. 

Pool Factor: Means, as of any Distribution Date, the quotient (rounded to the seventh decimal place) computed by
dividing (i) the Pool Balance by (ii) the original aggregate face amount of the Applicable Certificates. The Pool Factor as of any Distribution Date shall be computed after giving effect to any special distribution with respect to unused
Deposits, payment of principal of the Series B Equipment Notes or payment with respect to other Trust Property and the distribution thereof to be made on that date. 

Prospectus Supplement: Means the final Prospectus Supplement dated May 9, 2018 relating to the offering of the
Applicable Certificates. 
 Ratings Confirmation: Has the meaning specified in the Intercreditor Agreement. 

Related Pass Through Trust Agreement: Means the Basic Agreement, as supplemented by the Trust Supplement No. 2018-1B-S dated as of the date hereof relating to the United Airlines Pass Through Trust
2018-1B-S and entered into by the Company and the Related Trustee, which agreement becomes effective upon the execution and delivery of the Assignment and Assumption
Agreement pursuant to Section 7.01 of this Trust Supplement. 
 Related Trust: Means the United Airlines Pass
Through Trust 2018-1B-S, to be formed under the Related Pass Through Trust Agreement. 

Related Trustee: Means the trustee under the Related Pass Through Trust Agreement. 

Remaining Aircraft: Mean each Applicable Aircraft other than a Financed Aircraft. 

Scheduled Closing Date: Has the meaning specified in the NPA. 

Scheduled Payment: Means, with respect to any Series B Equipment Note, (i) any payment of principal or interest on
such Series B Equipment Note (other than any such payment which is not in fact received by the Trustee or the Subordination Agent within five days of the date on which such payment is scheduled to be made) or (ii) any payment


  
 10 







 
of interest on the Applicable Certificates with funds drawn under the Liquidity Facility, which payment in any such case represents the installment of principal on such Series B Equipment Note at
the stated maturity of such installment, the payment of regularly scheduled interest accrued on the unpaid principal amount of such Series B Equipment Note, or both; provided, however, that any payment of principal, premium (including
Make-Whole Amount), if any, or interest resulting from the redemption or purchase of any Series B Equipment Note shall not constitute a Scheduled Payment. 

Series B Equipment Notes: Means all of the Series B Equipment Notes issued under the Indentures. 

Special Payment: Means any payment (other than a Scheduled Payment) in respect of, or any proceeds of, any Series B
Equipment Note or Collateral (as defined in each Indenture). 
 Substitute Aircraft: Has the meaning specified in the
NPA. 
 Transfer Date: Has the meaning specified in Section 7.01 of this Trust Supplement. 

Triggering Event: Has the meaning assigned to such term in the Intercreditor Agreement. 

Trust Property: Means (i) subject to the Intercreditor Agreement, the Series B Equipment Notes held as the property
of the Applicable Trust, all monies at any time paid thereon or in respect thereof and all monies due and to become due thereunder, (ii) funds from time to time deposited in the Certificate Account and the Special Payments Account and, subject
to the Intercreditor Agreement, any proceeds from the sale by the Trustee pursuant to Article VI of the Basic Agreement of any Series B Equipment Note and (iii) all rights of the Applicable Trust and the Trustee, on behalf of the
Applicable Trust, under the Intercreditor Agreement, the Escrow Agreement, the NPA and the Liquidity Facility, including, without limitation, all rights to receive certain payments thereunder, and all monies paid to the Trustee on behalf of the
Applicable Trust pursuant to the Intercreditor Agreement or the Liquidity Facility, provided that rights with respect to the Deposits or under the Escrow Agreement, except for the right to direct withdrawals for the purchase of Series B Equipment
Notes to be held herein, will not constitute Trust Property. 
 Trust Supplement: Has the meaning specified in the
first paragraph of this trust supplement. 
 Trustee: Has the meaning specified in the first paragraph of this Trust
Supplement. 
 Underwriters: Means, collectively, Credit Suisse Securities (USA) LLC, Citigroup Global Markets Inc.,
Goldman Sachs & Co. LLC, Deutsche Bank Securities Inc., Morgan Stanley & Co. LLC, Barclays Capital Inc. Merrill Lynch, Pierce, Fenner & Smith Incorporated, BNP Paribas Securities Corp., Credit Agricole Securities (USA)
Inc., J.P. Morgan Securities LLC, Standard Chartered Bank and Wells Fargo Securities, LLC. 

  
 11 







 Underwriting Agreement: Means the Underwriting Agreement related to the
Applicable Certificates dated May 9, 2018 among Credit Suisse Securities (USA) LLC and Citigroup Global Markets Inc., as representatives of the several Underwriters, the Company and the Depositary, as the same may be amended, supplemented or
otherwise modified from time to time in accordance with its terms. 
 United Bankruptcy Event: Has the meaning
specified in the Intercreditor Agreement. 
 ARTICLE III 

DISTRIBUTIONS; STATEMENTS TO CERTIFICATEHOLDERS 

Section 3.01. Statements to Applicable Certificateholders. (a) On each Distribution Date, the Trustee will include with each
distribution to Applicable Certificateholders of a Scheduled Payment or Special Payment, as the case may be, a statement setting forth the information provided below (in the case of a Special Payment, reflecting in part the information provided by
the Escrow Paying Agent under the Escrow Agreement). Such statement shall set forth (per $1,000 face amount Applicable Certificate as to (ii), (iii), (iv) and (v) below) the following information: 

(i) The aggregate amount of funds distributed on such Distribution Date under the Agreement and under the Escrow Agreement,
indicating the amount allocable to each source, including any portion thereof paid by the Liquidity Provider; 
 (ii) The
amount of such distribution under the Agreement allocable to principal and the amount allocable to premium (including Make-Whole Amount), if any; 

(iii) The amount of such distribution under the Agreement allocable to interest; 

(iv) The amount of such distribution under the Escrow Agreement allocable to interest; 

(v) The amount of such distribution under the Escrow Agreement allocable to unused Deposits, if any; and 

(vi) The Pool Balance and the Pool Factor. 

With respect to the Applicable Certificates registered in the name of a Clearing Agency or its nominee, on the Record Date prior to each
Distribution Date, the Trustee will request that such Clearing Agency post on its Internet bulletin board a securities position listing setting forth the names of all Clearing Agency Participants reflected on such Clearing Agency’s books as
holding interests in the Applicable Certificates on such Record Date. On each Distribution Date, the Trustee will mail to each such Clearing Agency Participant the statement described above and will make available additional copies as requested by
such Clearing Agency Participant for forwarding to holders of interests in the Applicable Certificates. 

  
 12 







 (b) Within a reasonable period of time after the end of each calendar year but not later than the
latest date permitted by law, the Trustee shall furnish to each Person who at any time during such calendar year was an Applicable Certificateholder of record a statement containing the sum of the amounts determined pursuant to clauses (a)(i),
(a)(ii), (a)(iii), (a)(iv) and (a)(v) above for such calendar year or, in the event such Person was an Applicable Certificateholder of record during a portion of such calendar year, for such portion of such year, and such other items as are readily
available to the Trustee and which an Applicable Certificateholder shall reasonably request as necessary for the purpose of such Applicable Certificateholder’s preparation of its U.S. federal income tax returns. Such statement and such other
items shall be prepared on the basis of information supplied to the Trustee by the Clearing Agency Participants and shall be delivered by the Trustee to such Clearing Agency Participants to be available for forwarding by such Clearing Agency
Participants to the holders of interests in the Applicable Certificates in the manner described in Section 3.01(a) of this Trust Supplement. 

(c) If the aggregate principal payments scheduled for a Regular Distribution Date prior to the Delivery Period Termination Date differ from the
amount thereof set forth for the Applicable Certificates on page S-38 of the Prospectus Supplement, by no later than the 15th day prior to such Regular Distribution Date, the Trustee shall mail written notice
of the actual amount of such scheduled payments to the Applicable Certificateholders of record as of a date within 15 Business Days prior to the date of mailing. 

(d) Promptly following (i) the Delivery Period Termination Date, if there has been any change in the information set forth in clauses
(y) and (z) below from that set forth on page S-38 of the Prospectus Supplement, and (ii) the date of any early redemption of, or any default in the payment of principal or interest in respect of,
any of the Series B Equipment Notes held in the Applicable Trust, or any Final Withdrawal, the Trustee shall furnish to Applicable Certificateholders of record on such date a statement setting forth (x) the expected Pool Balances for each
subsequent Regular Distribution Date following the Delivery Period Termination Date, (y) the related Pool Factors for such Regular Distribution Dates and (z) the expected principal payment schedule of the Series B Equipment Notes, in the
aggregate, held as Trust Property at the date of such notice. With respect to the Applicable Certificates registered in the name of a Clearing Agency, on the Delivery Period Termination Date, the Trustee will request from such Clearing Agency a
securities position listing setting forth the names of all Clearing Agency Participants reflected on such Clearing Agency’s books as holding interests in the Applicable Certificates on such date. The Trustee will mail to each such Clearing
Agency Participant the statement described above and will make available additional copies as requested by such Clearing Agency Participant for forwarding to holders of interests in the Applicable Certificates. 

(e) The Trustee shall provide promptly to the Applicable Certificateholders all material
non-confidential information received by the Trustee from the Company. 
 (f) This Section 3.01
supersedes and replaces Section 4.03 of the Basic Agreement, with respect to the Applicable Trust. 

  
 13 







 Section 3.02. Special Payments Account. (a) The Trustee shall establish and
maintain on behalf of the Applicable Certificateholders a Special Payments Account as one or more accounts, which shall be non-interest bearing except as provided in Section 4.04 of the Basic Agreement.
The Trustee shall hold the Special Payments Account in trust for the benefit of the Applicable Certificateholders and shall make or permit withdrawals therefrom only as provided in the Agreement. On each day when one or more Special Payments are
made to the Trustee under the Intercreditor Agreement, the Trustee, upon receipt thereof, shall immediately deposit the aggregate amount of such Special Payments in the Special Payments Account. 

(b) This Section 3.02 supersedes and replaces Section 4.01(b) of the Basic Agreement in its entirety, with respect to the Applicable
Trust. 
 Section 3.03. Distributions from Special Payments Account. (a) On each Special Distribution Date with respect to
any Special Payment or as soon thereafter as the Trustee has confirmed receipt of any Special Payments due on the Series B Equipment Notes held (subject to the Intercreditor Agreement) in the Applicable Trust or realized upon the sale of such Series
B Equipment Notes, the Trustee shall distribute out of the Special Payments Account the entire amount of such Special Payment deposited therein pursuant to Section 3.02(a) of this Trust Supplement. There shall be so distributed to each
Applicable Certificateholder of record on the Record Date with respect to such Special Distribution Date (other than as provided in Section 7.01 of this Trust Supplement concerning the final distribution) by check mailed to such Applicable
Certificateholder, at the address appearing in the Register, such Applicable Certificateholder’s pro rata share (based on the Fractional Undivided Interest in the Applicable Trust held by such Applicable Certificateholder) of the total
amount in the Special Payments Account on account of such Special Payment, except that, with respect to Applicable Certificates registered on the Record Date in the name of a Clearing Agency (or its nominee), such distribution shall be made by wire
transfer in immediately available funds to the account designated by such Clearing Agency (or such nominee). 
 (b) The Trustee shall, at the
expense of the Company, cause notice of each Special Payment to be mailed to each Applicable Certificateholder at his address as it appears in the Register. In the event of redemption or purchase of Series B Equipment Notes held in the Applicable
Trust, such notice shall be mailed not less than 15 days prior to the Special Distribution Date for the Special Payment resulting from such redemption or purchase, which Special Distribution Date shall be the date of such redemption or purchase. In
the case of any other Special Payments, such notice shall be mailed as soon as practicable after the Trustee has confirmed that it has received funds for such Special Payment, stating the Special Distribution Date for such Special Payment which
shall occur not less than 15 days after the date of such notice and as soon as practicable thereafter. Notices with respect to a Special Payment mailed by the Trustee shall set forth: 

(i) The Special Distribution Date and the Record Date therefor (except as otherwise provided in Section 7.01 of this Trust
Supplement), 

  
 14 







 (ii) The amount of the Special Payment for each $1,000 face amount Applicable
Certificate and the amount thereof constituting principal, premium (including Make-Whole Amount), if any, and interest, 

(iii) The reason for the Special Payment, and 

(iv) If the Special Distribution Date is the same date as a Regular Distribution Date, the total amount to be received on such
date for each $1,000 face amount Applicable Certificate. 
 If the amount of premium (including Make-Whole Amount), if any, payable upon the
redemption or purchase of a Series B Equipment Note has not been calculated at the time that the Trustee mails notice of a Special Payment, it shall be sufficient if the notice sets forth the other amounts to be distributed and states that any
premium (including Make-Whole Amount) received will also be distributed. 
 If any redemption of the Series B Equipment Notes held in the
Applicable Trust is canceled, the Trustee, as soon as possible after learning thereof, shall cause notice thereof to be mailed to each Applicable Certificateholder at its address as it appears on the Register. 

(c) This Section 3.03 supersedes and replaces Section 4.02(b) and Section 4.02(c) of the Basic Agreement in their entirety, with
respect to the Applicable Trust. 
 Section 3.04. Limitation of Liability for Payments. Section 3.09 of the Basic Agreement
shall be amended, with respect to the Applicable Trust, by deleting the phrase “the Owner Trustees or the Owner Participants” in the second sentence thereof and adding in lieu thereof “the Liquidity Provider”. 

ARTICLE IV 
 DEFAULT 

Section 4.01. Purchase Rights of Certificateholders. (a) By acceptance of its Applicable Certificate, each Applicable
Certificateholder agrees that at any time after the occurrence and during the continuation of a Certificate Buyout Event: 

(i) So long as no Additional Certificateholder has elected to exercise its rights to purchase Certificates pursuant to, and
given notice of such election in accordance with, Section 4.01(a)(ii) (upon such election and notification thereof, the right specified in this Section 4.01(a)(i) shall be suspended and (x) upon consummation of such purchase pursuant
to such election, be terminated with respect to such Certificate Buyout Event, or (y) upon failure to consummate such purchase on the proposed purchase date, such right shall be reinstated), each Applicable Certificateholder (other than the
Company or any of its Affiliates) shall have the right to purchase, for the purchase price set forth in the Class AA Trust Agreement and in the Class A Trust Agreement, all, but not less than all, of the Class AA Certificates and the
Class A Certificates upon 15 days’ written notice to the Class AA Trustee, the Class A Trustee and each other Applicable Certificateholder, on the third Business Day next following the expiry of such 15-day notice period, provided 

  
 15 







 
that (A) if prior to the end of such 15-day period any other Applicable Certificateholder (other than the Company or any of its Affiliates) notifies
such purchasing Applicable Certificateholder that such other Applicable Certificateholder wants to participate in such purchase, then such other Applicable Certificateholder (other than the Company or any of its Affiliates) may join with the
purchasing Applicable Certificateholder to purchase all, but not less than all, of the Class AA Certificates and the Class A Certificates pro rata based on the Fractional Undivided Interest in the Applicable Trust held by each such
Applicable Certificateholder and (B) if prior to the end of such 15-day period any other Applicable Certificateholder fails to notify the purchasing Applicable Certificateholder of such other Applicable
Certificateholder’s desire to participate in such a purchase, then such other Applicable Certificateholder shall lose its right to purchase the Class AA Certificates and the Class A Certificates pursuant to this
Section 4.01(a)(i). 
 (ii) If any Additional Certificates are issued pursuant to one or more Additional Trusts, each
Additional Certificateholder (other than the Company or any of its Affiliates) shall have the right (which shall not expire upon any purchase of the Class AA Certificates and the Class A Certificates pursuant to clause (i) above) to
purchase all, but not less than all, of the Class AA Certificates, the Class A Certificates, the Applicable Certificates and any Additional Certificates ranked senior to the Additional Certificates held by the purchasing Additional
Certificateholders upon 15 days’ written notice to the Trustee, the Class AA Trustee, the Class A Trustee, any Additional Trustee with respect to Additional Certificates that rank senior to the Additional Certificates held by the
purchasing Additional Certificateholders and each other Additional Certificateholder of the same class, on the third Business Day next following the expiry of such 15-day notice period, provided that
(A) if prior to the end of such 15-day period any other Additional Certificateholder of such class (other than the Company or any of its Affiliates) notifies such purchasing Additional Certificateholder
that such other Additional Certificateholder wants to participate in such purchase, then such other Additional Certificateholder (other than the Company or any of its Affiliates) may join with the purchasing Additional Certificateholder to purchase
all, but not less than all, of the Class AA Certificates, the Class A Certificates, the Applicable Certificates and such senior Additional Certificates pro rata based on the Fractional Undivided Interest in the applicable Additional Trust
held by each such Additional Certificateholder and (B) if prior to the end of such 15-day period any other Additional Certificateholder of such class fails to notify the purchasing Additional
Certificateholder of such other Additional Certificateholder’s desire to participate in such a purchase, then such other Additional Certificateholder shall lose its right to purchase the Class AA Certificates, the Class A
Certificates, the Applicable Certificates and such senior Additional Certificates pursuant to this Section 4.01(a)(ii); and 

(iii) If any Refinancing Certificates are issued, each Refinancing Certificateholder shall have the same right (subject to the
same terms and conditions) to purchase Certificates pursuant to this Section 4.01(a) (and to receive notice in connection therewith) as the Certificateholders of the Class that such Refinancing Certificates refinanced. 

  
 16 







 The purchase price with respect to the Applicable Certificates shall be equal to the Pool Balance
of the Applicable Certificates, together with accrued and unpaid interest thereon to the date of such purchase, without premium (including Make-Whole Amount), but including any other amounts then due and payable to the Applicable Certificateholders
under the Agreement, the Intercreditor Agreement, the Escrow Agreement or any Note Document or on or in respect of the Applicable Certificates; provided, however, that no such purchase of Applicable Certificates shall be effective
unless the purchaser(s) shall certify to the Trustee that contemporaneously with such purchase, such purchaser(s) is (are) purchasing, pursuant to the terms of the Agreement and the Other Agreements, all of the Applicable Certificates, the
Class AA Certificates, the Class A Certificates and, if applicable, the Additional Certificates that rank senior to the Additional Certificates held by the purchasing Additional Certificateholder(s). Each payment of the purchase price of
the Applicable Certificates referred to in the first sentence hereof shall be made to an account or accounts designated by the Trustee and each such purchase shall be subject to the terms of this Section 4.01. Each Applicable Certificateholder
agrees by its acceptance of its Applicable Certificate that (at any time after the occurrence of a Certificate Buyout Event) it will, upon payment from Additional Certificateholder(s) or Refinancing Certificateholder(s), as the case may be, of the
purchase price set forth in the first sentence of this paragraph, (i) forthwith sell, assign, transfer and convey to the purchaser(s) thereof (without recourse, representation or warranty of any kind except for its own acts), all of the right,
title, interest and obligation of such Applicable Certificateholder in the Agreement, the Escrow Agreement, the Deposit Agreement, the Intercreditor Agreement, the Liquidity Facility, the NPA Amendment (and the NPA as Amended thereby) the Note
Documents and all Applicable Certificates and Escrow Receipts held by such Applicable Certificateholder (excluding all right, title and interest under any of the foregoing to the extent such right, title or interest is with respect to an obligation
not then due and payable as respects any action or inaction or state of affairs occurring prior to such sale) (and the purchaser shall assume all of such Applicable Certificateholder’s obligations under the Agreement, the Escrow Agreement, the
Deposit Agreement, the Intercreditor Agreement, the Liquidity Facility, the NPA Amendment (and the NPA as amended thereby), the Note Documents and all such Applicable Certificates and Escrow Receipts), (ii) if such purchase occurs after a record
date specified in Section 2.03 of the Escrow Agreement relating to the distribution of unused Deposits and/or accrued and unpaid interest on Deposits and prior to or on the related distribution date thereunder, forthwith turn over to the
purchaser(s) of its Applicable Certificate all amounts, if any, received by it on account of such distribution, and (iii) if such purchase occurs after a Record Date relating to any distribution and prior to or on the related Distribution Date,
forthwith turn over to the purchaser(s) of its Applicable Certificate all amounts, if any, received by it on account of such distribution. The Applicable Certificates will be deemed to be purchased on the date payment of the purchase price is made
notwithstanding the failure of the Applicable Certificateholders to deliver any Applicable Certificates and, upon such a purchase, (I) the only rights of the Applicable Certificateholders will be to deliver the Applicable Certificates to the
purchaser(s) and receive the purchase price for such Applicable Certificates and (II) if the purchaser(s) shall so request, such Applicable Certificateholder will comply with all the provisions of Section 3.04 of the Basic Agreement to
enable new Applicable Certificates to be issued to the purchaser in such denominations as it shall request. All charges and expenses in connection with the issuance of any such new Applicable Certificates shall be borne by the purchaser thereof.


  
 17 







 As used in this Section 4.01 and elsewhere in this Trust Supplement, the terms
“Additional Certificate”, “Additional Certificateholder”, “Additional Equipment Notes”, “Additional Trust”, “Class AA Certificate”, “Class AA Trust Agreement”, “Class AA
Trustee”, “Class A Certificate”, “Class A Trust Agreement”, “Class A Trustee”, “Refinancing Certificates”, “Refinancing Certificateholder”, “Refinancing Equipment Notes”
and “Refinancing Trust” shall have the respective meanings assigned to such terms in the Intercreditor Agreement. 
 (b) This
Section 4.01 supersedes and replaces Section 6.01(b) of the Basic Agreement, with respect to the Applicable Trust. 

Section 4.02. Amendment of Section 6.05 of the Basic Agreement. Section 6.05 of the Basic Agreement shall
be amended, with respect to the Applicable Trust, by deleting the phrase “and thereby annul any Direction given by such Certificateholders or the Trustee to such Loan Trustee with respect thereto,” set forth in the first sentence thereof.

 ARTICLE V 
 THE TRUSTEE 

Section 5.01. Delivery of Documents; Issuance Date and Delivery Dates. (a) The Trustee is hereby directed (i) to execute
and deliver the Intercreditor Agreement, the Escrow Agreement and the NPA Amendment (and the NPA as amended thereby) on or prior to the Class B Issuance Date, each in the form delivered to the Trustee by the Company, and (ii) subject to
the respective terms thereof, to perform its obligations thereunder. Upon request of the Company and the satisfaction or waiver of the closing conditions specified in the Underwriting Agreement, the Trustee shall execute, deliver, authenticate,
issue and sell Applicable Certificates in authorized denominations equaling in the aggregate the amount set forth, with respect to the Applicable Trust, in Schedule I to the Underwriting Agreement evidencing the entire ownership interest in the
Applicable Trust, which amount equals the maximum aggregate principal amount of Series B Equipment Notes which may be purchased by the Trustee pursuant to the NPA. Except as provided in Sections 3.03, 3.04, 3.05 and 3.06 of the Basic Agreement, the
Trustee shall not execute, authenticate or deliver Applicable Certificates in excess of the aggregate amount specified in this paragraph. The provisions of this Section 5.01(a) supersede and replace the first sentence of Section 3.02(a) of
the Basic Agreement, with respect to the Applicable Trust. 
 (b) (i) On the Class B Issuance Date, the Trustee shall, subject to
satisfaction of the applicable conditions specified in the NPA with respect to purchase of Series B Equipment Notes relating to the Financed Aircraft, (A) purchase such Series B Equipment Notes relating to such Financed Aircraft with a portion
of the proceeds of the Applicable Certificates (without such proceeds so used on the Class B Issuance Date to purchase such Series B Equipment Notes being deposited under the Deposit Agreement), and (B) enter into and perform its
obligations under the applicable Participation Agreement Amendment (and Participation Agreement as amended thereby) and cause such other certificates, documents and legal opinions relating to the Trustee to be duly delivered as required by the NPA.


  
 18 







 (ii) After the Class B Issuance Date, the Company may deliver from time to time to the
Trustee a Closing Notice relating to one or more Series B Equipment Notes (not otherwise having been purchased on the Class B Issuance Date). After receipt of a Closing Notice and in any case no later than one Business Day prior to a Scheduled
Closing Date as to which such Closing Notice relates (the “Applicable Closing Date”), the Trustee shall (as and when specified in the Closing Notice) instruct the Escrow Agent to provide a Notice of Purchase Withdrawal to the
Depositary requesting (A) the withdrawal of one or more Deposits on the Applicable Closing Date in accordance with and to the extent permitted by the terms of the Escrow Agreement and the Deposit Agreement and (B) the payment of all, or a
portion, of such Deposit or Deposits in an amount equal in the aggregate to the purchase price of such Series B Equipment Notes to or on behalf of the Company, all as shall be described in the Closing Notice. The Trustee shall (as and when specified
in such Closing Notice), subject to the conditions set forth in Section 2 of the NPA, enter into and perform its obligations under the Participation Agreement specified in such Closing Notice (the “Applicable Participation
Agreement”) and cause such certificates, documents and legal opinions relating to the Trustee to be duly delivered as required by the Applicable Participation Agreement. If at any time prior to the Applicable Closing Date, the Trustee
receives a notice of postponement pursuant to Section 1(e) or 1(f) of the NPA, then the Trustee shall give the Depositary (with a copy to the Escrow Agent) a notice of cancellation of such Notice of Purchase Withdrawal relating to such Deposit
or Deposits on such Applicable Closing Date. Upon satisfaction of the conditions specified in the NPA and the Applicable Participation Agreement, the Trustee shall purchase the applicable Series B Equipment Notes with the proceeds of the withdrawals
of one or more Deposits made on the Applicable Closing Date in accordance with the terms of the Deposit Agreement and the Escrow Agreement. Amounts withdrawn from such Deposit or Deposits in excess of the purchase price of the Series B Equipment
Notes or to the extent not applied on the Applicable Closing Date to the purchase price of the Series B Equipment Notes, shall be re-deposited by the Trustee with the Depositary on the Applicable Closing Date
in accordance with the terms of the Deposit Agreement. 
 (iii) The purchase price of any Series B Equipment Notes shall equal the principal
amount of such Series B Equipment Notes. The provisions of this Section 5.01(b) supersede and replace the provisions of Section 2.02 of the Basic Agreement with respect to the Applicable Trust, and all provisions of the Basic Agreement
relating to Postponed Notes and Section 2.02 of the Basic Agreement shall not apply to the Applicable Trust. 
 (c) The Trustee
acknowledges its acceptance of all right, title and interest in and to the Trust Property to be acquired pursuant to Section 5.01(b) of this Trust Supplement, the NPA and each Participation Agreement, and declares that it holds and will hold
such right, title and interest for the benefit of all present and future Applicable Certificateholders, upon the trusts set forth in the Agreement. By its acceptance of an Applicable Certificate, each initial Applicable Certificateholder, as a
grantor of the Applicable Trust, joins with the Trustee in the creation of the Applicable Trust. The provisions of this Section 5.01(c) supersede and replace the provisions of Section 2.03 of the Basic Agreement, with respect to the
Applicable Trust. 

  
 19 







 Section 5.02. Withdrawal of Deposits. If any Deposits remain outstanding on the
Business Day next succeeding the Cut-off Date, the Trustee shall promptly give the Escrow Agent notice that the Trustee’s obligation to purchase Series B Equipment Notes under the NPA has terminated and
instruct the Escrow Agent to provide a notice of Final Withdrawal to the Depositary substantially in the form of Exhibit B to the Deposit Agreement (the “Final Withdrawal Notice”). 

Section 5.03. The Trustee. (a) Subject to Section 5.04 of this Trust Supplement and Section 7.15 of the Basic
Agreement, the Trustee shall not be responsible in any manner whatsoever for or in respect of the validity or sufficiency of this Trust Supplement, the Deposit Agreement, the NPA Amendment (and the NPA as amended thereby) or the Escrow Agreement or
the due execution hereof or thereof by the Company or the other parties thereto (other than the Trustee), or for or in respect of the recitals and statements contained herein or therein, all of which recitals and statements are made solely by the
Company, except that the Trustee hereby represents and warrants that each of this Trust Supplement, the Basic Agreement, each Applicable Certificate, the Intercreditor Agreement, the NPA Amendment (and the NPA as amended thereby) and the Escrow
Agreement has been executed and delivered by one of its officers who is duly authorized to execute and deliver such document on its behalf. 

(b) Except as herein otherwise provided and except during the continuation of an Event of Default in respect of the Applicable Trust created
hereby, 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 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 Agreement, as fully to all intents as if the same were herein set forth at length. 

Section 5.04. Representations and Warranties of the Trustee. The Trustee hereby represents and warrants that: 

(a) The Trustee has full power, authority and legal right to execute, deliver and perform this Trust Supplement, the
Intercreditor Agreement, the Escrow Agreement, the NPA Amendment (and the NPA as amended thereby) and the Note Documents to which it is or is to become a party and has taken all necessary action to authorize the execution, delivery and performance
by it of this Trust Supplement, the Intercreditor Agreement, the Escrow Agreement, the NPA Amendment (and the NPA as amended thereby) and the Note Documents to which it is or is to become a party; 

(b) The execution, delivery and performance by the Trustee of this Trust Supplement, the Intercreditor Agreement, the Escrow
Agreement, the NPA Amendment (and the NPA as amended thereby) and the Note Documents to which it is or is to become a party (i) will not violate any provision of any United States federal law or the law of the state of the United States where
it is located governing the banking and trust powers of the Trustee or any order, writ, judgment, or decree of any court, arbitrator or governmental authority applicable to the Trustee or any of its assets, (ii) will not violate any provision
of the articles of association or by-laws of the Trustee, and (iii) will not violate any provision of, or constitute, with or without notice or lapse of time, a default under, or result in the creation or
imposition of any lien on any properties included in the Trust Property pursuant to the provisions of any mortgage, indenture, contract, agreement 

  
 20 







 
or other undertaking to which it is a party, which violation, default or lien could reasonably be expected to have an adverse effect on the Trustee’s performance or ability to perform its
duties hereunder or thereunder or on the transactions contemplated herein or therein; 
 (c) The execution, delivery and
performance by the Trustee of this Trust Supplement, the Intercreditor Agreement, the Escrow Agreement, the NPA Amendment (and the NPA as amended thereby) and the Note Documents to which it is or is to become a party will not require the
authorization, consent, or approval of, the giving of notice to, the filing or registration with, or the taking of any other action in respect of, any governmental authority or agency of the United States or the state of the United States where it
is located regulating the banking and corporate trust activities of the Trustee; and 
 (d) This Trust Supplement, the
Intercreditor Agreement, the Escrow Agreement, the NPA Amendment (and the NPA as amended thereby) and the Note Documents to which it is or is to become a party have been, or will be, as applicable, duly executed and delivered by the Trustee and
constitute, or will constitute, as applicable, the legal, valid and binding agreements of the Trustee, enforceable against it in accordance with their respective terms; provided, however, that enforceability may be limited by
(i) applicable bankruptcy, insolvency, reorganization, moratorium or similar laws affecting the rights of creditors generally and (ii) general principles of equity. 

Section 5.05. Trustee Liens. The Trustee in its individual capacity agrees, in addition to the agreements contained in
Section 7.17 of the Basic Agreement, that it will at its own cost and expense promptly take any action as may be necessary to duly discharge and satisfy in full any Trustee’s Liens on or with respect to the Trust Property which is
attributable to the Trustee in its individual capacity and which is unrelated to the transactions contemplated by the Intercreditor Agreement or the NPA. 

ARTICLE VI 
 ADDITIONAL AMENDMENT;
SUPPLEMENTAL AGREEMENTS 
 Section 6.01. Amendment of Section 5.02 of the Basic Agreement. Section 5.02
of the Basic Agreement shall be amended, with respect to the Applicable Trust, by (i) replacing the phrase “of the Note Documents and of this Agreement” set forth in paragraph (b) thereof with the phrase “of the Note
Documents, of the NPA and of this Agreement” and (ii) replacing the phrase “of this Agreement and any Note Document” set forth in the last paragraph of Section 5.02 with the phrase “of this Agreement, the NPA and any
Note Document”. 
 Section 6.02. Supplemental Agreements without Consent of Applicable Certificateholders. Without
limitation of Section 9.01 of the Basic Agreement, under the terms of, and subject to the limitations contained in, Section 9.01 of the Basic Agreement, the Company may (but will not be required to), and the Trustee (subject to
Section 9.03 of the Basic Agreement) shall, at the Company’s request, at any time and from time to time: 

  
 21 







 (i) Enter into one or more agreements supplemental to the Escrow Agreement, the NPA or the
Deposit Agreement for any of the purposes set forth in clauses (1) through (9) of such Section 9.01, and (without limitation of the foregoing or Section 9.01 of the Basic Agreement) (a) clauses (2) and (3) of such
Section 9.01 shall also be deemed to include the Company’s obligations under (in the case of clause (2)), and the Company’s rights and powers conferred by (in the case of clause (3)), the NPA, and (b) references in clauses (4),
(6) and (7) of such Section 9.01 to “any Intercreditor Agreement or any Liquidity Facility” shall also be deemed to refer to “the Intercreditor Agreement, the Liquidity Facility, the Escrow Agreement, the NPA or the Deposit
Agreement”, 
 (ii) Enter into one or more agreements supplemental to the Agreement, the Intercreditor Agreement or the NPA to provide
for the formation of one or more Additional Trusts, the issuance of Additional Certificates, the purchase by an Additional Trust (if any) of applicable Additional Equipment Notes and other matters incidental thereto or otherwise contemplated by
Section 2.01(b) of the Basic Agreement, subject to the provisions of Section 4(a)(vi) of the NPA and Section 9.1(d) of the Intercreditor Agreement, and 

(iii) Enter into one or more agreements supplemental to the Agreement to provide for the formation of one or more Refinancing Trusts, the
issuance of Refinancing Certificates, the purchase by any Refinancing Trust of applicable Refinancing Equipment Notes and other matters incidental thereto or as otherwise contemplated by Section 2.01(b) of the Basic Agreement, subject to the
provisions of Section 4(a)(vi) of the NPA and Section 9.1(c) of the Intercreditor Agreement. 
 Section 6.03. Supplemental
Agreements with Consent of Applicable Certificateholders. Without limitation of Section 9.02 of the Basic Agreement, the provisions of Section 9.02 of the Basic Agreement shall apply to agreements or amendments for the purpose of
adding any provisions to or changing in any manner or eliminating any of the provisions of the Escrow Agreement, the Deposit Agreement, the Liquidity Facility or the NPA or modifying in any manner the rights and obligations of the Applicable
Certificateholders under the Escrow Agreement, the Deposit Agreement, the Liquidity Facility or the NPA; provided that the provisions of Section 9.02(1) of the Basic Agreement shall be deemed to include reductions in any manner of, or delay in
the timing of, any receipt by the Applicable Certificateholders of payments upon the Deposits. 
 Section 6.04. Consent of Holders
of Certificates Issued under Other Trusts. Notwithstanding any provision in Section 6.02 or Section 6.03 of this Trust Supplement to the contrary, no amendment or modification of Section 4.01 of this Trust Supplement shall be
effective unless the trustee for each Class of Certificates affected by such amendment or modification shall have consented thereto. 

  
 22 







 ARTICLE VII 

TERMINATION OF TRUST 

Section 7.01. Termination of the Applicable Trust. (a) The respective obligations and responsibilities of the Company and the
Trustee with respect to the Applicable Trust shall terminate upon the earlier of (A) the completion of the assignment, transfer and discharge described in the first sentence of the immediately following paragraph and (B) the distribution
to all Applicable Certificateholders and the Trustee 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; provided, however, that in no
event shall the Applicable Trust continue beyond one hundred ten (110) years following the date of the execution of this Trust Supplement. 

Upon the earlier of (i) the first Business Day following August 31, 2018 or, if later, the fifth Business Day following the Delivery
Period Termination Date and (ii) the fifth Business Day following the date on which a Triggering Event occurs (such date, the “Transfer Date”), or, if later, the date on which all of the conditions set forth in the immediately
following sentence have been satisfied, the Trustee is hereby directed (subject only to the immediately following sentence) to, and the Company shall direct the institution that will serve as the Related Trustee under the Related Pass Through Trust
Agreement to, execute and deliver the Assignment and Assumption Agreement, pursuant to which the Trustee shall assign, transfer and deliver all of the Trustee’s right, title and interest to the Trust Property to the Related Trustee under the
Related Pass Through Trust Agreement. The Trustee and the Related Trustee shall execute and deliver the Assignment and Assumption Agreement upon the satisfaction of the following conditions: 

(i) The Trustee, the Related Trustee and each of the Rating Agencies then rating the Applicable Certificates shall have received an
Officer’s Certificate and an Opinion of Counsel dated the date of the Assignment and Assumption Agreement and each satisfying the requirements of Section 1.02 of the Basic Agreement, which Opinion of Counsel shall be substantially to the
effect set forth below and may be relied upon by the Beneficiaries (as defined in the Assignment and Assumption Agreement): 

(I) Upon the execution and delivery thereof by the parties thereto in accordance with the terms of the Agreement and the
Related Pass Through Trust Agreement, the Assignment and Assumption Agreement will constitute the valid and binding obligation of each of the parties thereto enforceable against each such party in accordance with its terms; 

(II) Upon the execution and delivery of the Assignment and Assumption Agreement in accordance with the terms of the Agreement
and the Related Pass Through Trust Agreement, each of the Applicable Certificates then Outstanding will be entitled to the benefits of the Related Pass Through Trust Agreement; 

(III) The Related Trust is not required to be registered as an investment company under the Investment Company Act of 1940, as
amended; 
 (IV) The Related Pass Through Trust Agreement constitutes the valid and binding obligation of the Company
enforceable against the Company in accordance with its terms; and 

  
 23 







 (V) Neither the execution and delivery of the Assignment and Assumption Agreement
in accordance with the terms of the Agreement and the Related Pass Through Trust Agreement, nor the consummation by the parties thereto of the transactions contemplated to be consummated thereunder on the date thereof, will violate any law or
governmental rule or regulation of the State of New York or the United States of America known to such counsel to be applicable to the transactions contemplated by the Assignment and Assumption Agreement. 

(ii) The Trustee and the Company shall have received (x) a copy of the articles of incorporation and bylaws of the Related
Trustee certified as of the Transfer Date by the Secretary or Assistant Secretary of such institution and (y) a copy of the filing (including all attachments thereto) made by the institution serving as the Related Trustee with the Office of the
Superintendent, State of New York Banking Department for the qualification of the Related Trustee under Section 131(3) of the New York Banking Law, if applicable to such Related Trustee. 

Upon the execution of the Assignment and Assumption Agreement by the parties thereto, the Applicable Trust shall be terminated, the Applicable
Certificateholders shall receive beneficial interests in the Related Trust in exchange for their interests in the Applicable Trust equal to their respective beneficial interests in the Applicable Trust, and the Outstanding Applicable Certificates
representing Fractional Undivided Interests in the Applicable Trust shall be deemed for all purposes of the Agreement and the Related Pass Through Trust Agreement, without further signature or action of any party or Applicable Certificateholder, to
be certificates representing the same fractional undivided interests in the Related Trust and its trust property. By acceptance of its Applicable Certificate, each Applicable Certificateholder consents to such assignment, transfer and delivery of
the Trust Property to the trustee of the Related Trust upon the execution and delivery of the Assignment and Assumption Agreement. 
 In
connection with the occurrence of the event set forth in clause (B) above of the first paragraph of this Section 7.01(a), notice of such termination, specifying the Distribution Date upon which the Applicable Certificateholders may
surrender their Applicable Certificates to the Trustee for payment of the final distribution and cancellation, shall be mailed promptly by the Trustee to Applicable Certificateholders not earlier than the 60th day and not later than the 15th day
next preceding such final Distribution Date specifying (A) the Distribution Date upon which the proposed final payment of the Applicable Certificates will be made upon presentation and surrender of Applicable Certificates at the office or
agency of the Trustee therein specified, (B) the amount of any such proposed final payment, and (C) that the Record Date otherwise applicable to such Distribution Date is not applicable, payments being made only upon presentation and
surrender of the Applicable Certificates at the office or agency of the Trustee therein specified. The Trustee shall give such notice to the Registrar at the time such notice is given to Applicable Certificateholders. Upon presentation and surrender
of the Applicable Certificates in accordance with such notice, the Trustee shall cause to be distributed to Applicable Certificateholders such final payments. 

  
 24 







 In the event that all of the Applicable Certificateholders shall not surrender their Applicable
Certificates for cancellation within six months after the date specified in the above-mentioned written notice, the Trustee shall give a second written notice to the remaining Applicable Certificateholders to
surrender their Applicable Certificates for cancellation and receive the final distribution with respect thereto. No additional interest shall accrue on the Applicable Certificates after the Distribution Date specified in the first written notice.
In the event that any money held by the Trustee for the payment of distributions on the Applicable Certificates shall remain unclaimed for two years (or such lesser time as the Trustee shall be satisfied, after sixty days’ notice from the
Company, is one month prior to the escheat period provided under applicable law) after the final distribution date with respect thereto, the Trustee shall pay to each Loan Trustee the appropriate amount of money relating to such Loan Trustee and
shall give written notice thereof to the Company. 
 (b) The provisions of this Section 7.01 supersede and replace the provisions of
Section 11.01 of the Basic Agreement in its entirety, with respect to the Applicable Trust. 
 ARTICLE VIII 

MISCELLANEOUS PROVISIONS 

Section 8.01. 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. All replacements of provisions of, and other
modifications of the Basic Agreement set forth in this Trust Supplement are solely with respect to the Applicable Trust. 

Section 8.02. GOVERNING LAW. THE AGREEMENT AND, UNTIL THE TRANSFER DATE, THE APPLICABLE CERTIFICATES SHALL BE GOVERNED BY AND
CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF DELAWARE. THIS SECTION 8.02 SUPERSEDES AND REPLACES SECTION 12.05 OF THE BASIC AGREEMENT, WITH RESPECT TO THE APPLICABLE TRUST. 

Section 8.03. 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. 
 Section 8.04. Intention of
Parties. The parties hereto intend that the Applicable Trust be classified for U.S. federal income tax purposes as a grantor trust under Subpart E, Part I of Subchapter J of the Internal Revenue Code of 1986, as amended, and not as a trust or
association taxable as a corporation or as a partnership. Each Applicable Certificateholder and Investor, by its acceptance of its Applicable Certificate or a beneficial interest therein, agrees to treat the Applicable Trust as a grantor trust for
all U.S. federal, state and local income tax purposes. The powers granted and obligations undertaken pursuant to the Agreement shall be so construed so as to further such intent. 

  
 25 







 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 AIRLINES, INC.
		
	By:	 	 /s/ Ted Davidson

		 	Name: Ted Davidson
		 	Title:   Vice President Procurement
	
	 WILMINGTON TRUST, NATIONAL ASSOCIATION,

as Trustee

		
	By:	 	 /s/ Jacqueline Solone

		 	Name: Jacqueline Solone
		 	Title:   Vice President


 Signature Page to Class B-O Trust Supplement 18-1 






 EXHIBIT A 

FORM OF CERTIFICATE 
 Certificate 

No.              

[Unless this certificate is presented by an authorized representative of The Depository Trust Company, a New York corporation
(“DTC”), to Issuer or its agent for registration of transfer, exchange or payment, and any certificate issued 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 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 the
registered owner hereof, Cede & Co., has an interest herein.]* 
 UNITED
AIRLINES PASS THROUGH TRUST 2018-1B-O 
 United Airlines Pass
Through Certificate, Series 2018-1B-O 
 Class B Issuance
Date: May 23, 2018 
 Final Maturity Date: September 1, 2027 

Evidencing A Fractional Undivided Interest In The United Airlines Pass Through Trust 2018-1B-O The Property Of Which Shall Include Certain Equipment Notes Each Secured By An Aircraft Owned By United Airlines, Inc. 

$[            ] Fractional Undivided Interest 

representing .000443009% of the Trust per $1,000 face amount 

THIS CERTIFIES THAT
                    , for value received, is the registered owner of a
$                    
(                                         
                                DOLLARS) Fractional Undivided Interest in the United
Airlines Pass Through Trust 2018-1B-O (the “Trust”) created by Wilmington Trust, National Association, as trustee (the “Trustee”),
pursuant to a Pass Through Trust Agreement, dated as of October 3, 2012 (the “Basic Agreement”), between the Trustee and United Airlines, Inc. (formerly known as Continental Airlines, Inc.), a Delaware corporation (the
“Company”), as supplemented by Trust Supplement No. 2018-1B-O thereto, dated as of May 23, 2018 (the “Trust Supplement” and,
together with 
  

	* 	 This legend to appear on Book-Entry Certificates to be deposited with the Depository Trust Company.




  
 A-1 







 
the Basic Agreement, the “Agreement”), between the Trustee and 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 Pass Through Certificates, Series 2018-1B-O” (herein called 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 holder of this Certificate (the “Certificateholder” and, together with all other holders of Certificates issued by the Trust, the “Certificateholders”) assents to and agrees
to be bound by the provisions of the Agreement and the Intercreditor Agreement. The property of the Trust includes certain Series B Equipment Notes and all rights of the Trust to receive payments under the Intercreditor Agreement and the Liquidity
Facility (the “Trust Property”). Each issue of the Series B Equipment Notes is secured by, among other things, a security interest in an 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 other separate trust established pursuant to the terms of the Basic Agreement for any other series of certificates issued pursuant thereto. 

Subject to and in accordance with the terms of the Agreement and the Intercreditor Agreement, from funds then available to the Trustee, there
will be distributed on March 1 and September 1 of each year (a “Regular Distribution Date”) commencing on September 1, 2018, to the Person in whose name this Certificate is registered at the close of business on the 15th day
preceding the Regular Distribution Date, an amount in respect of the Scheduled Payments on the Series B Equipment 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 and the Intercreditor Agreement, in the event that Special
Payments on the Series B Equipment 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 Series B Equipment 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
immediately following Business Day with the same force and effect as if made on such Regular Distribution Date or Special Distribution Date and no 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. 
 Distributions on this Certificate will
be made by the Trustee by check mailed to the Person entitled thereto, without presentation or surrender of this Certificate or the making of any notation hereon, except that with respect to Certificates registered on the Record Date in the name of
a Clearing Agency (or its nominee) such distribution shall be made by wire transfer. Except as otherwise provided in the Agreement and notwithstanding the above, the final distribution on this Certificate will 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. 

  
 A-2 







 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 affiliate thereof. The Certificates are limited in right of 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 will 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, privileges, 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 Undivided 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 set forth therein, 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, 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 will be issued to the designated transferee or transferees. 

Under certain circumstances set forth in Section 7.01 of the Trust Supplement, all of the Trustee’s right, title and interest to the
Trust Property may be assigned, transferred and delivered to the Related Trustee of the Related Trust pursuant to the Assignment and Assumption Agreement. Upon the effectiveness of such Assignment and Assumption Agreement (the
“Transfer”), the Trust shall be terminated, the Certificateholders shall receive beneficial interests in the Related Trust in exchange for their interests in the Trust equal to their respective beneficial


  
 A-3 







 
interests in the Trust, the Certificates representing Fractional Undivided Interests in the Trust shall be deemed for all purposes of the Agreement and the Related Pass Through Trust Agreement to
be certificates representing the same fractional undivided interests in the Related Trust and its trust property. Each Certificateholder, by its acceptance of this Certificate or a beneficial interest herein, agrees to be bound by the Assignment and
Assumption Agreement and subject to the terms of the Related Pass Through Trust Agreement as a Certificateholder thereunder. From and after the Transfer, unless and to the extent the context otherwise requires, references herein to the Trust, the
Agreement and the Trustee shall constitute references to the Related Trust, the Related Pass Through Trust Agreement and trustee of the Related Trust, respectively. 

The Certificates are issuable only as registered Certificates without coupons in minimum denominations of $1,000 Fractional Undivided Interest
and integral multiples thereof, except that one Certificate may be issued in a different denomination. 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. 

No service charge will be made for any such registration of transfer or exchange, but the Trustee shall require payment of a sum sufficient to
cover any tax or governmental charge payable in connection therewith. 
 Each Certificateholder and Investor, by its acceptance of this
Certificate or a beneficial interest herein, agrees to treat the Trust as a grantor trust for all U.S. federal, state and local income tax purposes. 

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. 

Any Person acquiring or accepting this Certificate or an interest herein will, by such acquisition or acceptance, be deemed to have
represented and warranted to and for the benefit of the Company that either: (i) no assets of an employee benefit plan subject to Title I of the Employee Retirement Income Security Act of 1974, as amended (“ERISA”), a plan
subject to Section 4975 of the Internal Revenue Code of 1986, as amended (the “Code”), or a governmental, church or foreign plan subject to a law that is similar to Title I of ERISA or Section 4975 of the Code (a
“Similar Law Plan”) have been used to purchase or hold this Certificate or an interest herein or (ii) the purchase and holding of this Certificate or an interest herein either (a) in the case of assets of an employee
benefit plan subject to Title I of ERISA or a plan subject to Section 4975 of the Code, are exempt from the prohibited transaction restrictions of ERISA and the Code pursuant to one or more prohibited transaction statutory or administrative
exemptions or (b) in the case of assets of a Similar Law Plan, will not violate any similar state, local or foreign law. 

  
 A-4 







 Any Person who is an employee benefit plan subject to Title I of ERISA, a plan subject to
Section 4975 of the Code, or an entity whose underlying assets are deemed to include “plan assets” by reason of such a plan’s investment in such entity (a “Benefit Plan Investor”) and is acquiring or accepting
this Certificate or an interest herein will, by such acquisition or acceptance, be deemed to have represented and warranted to and for the benefit of the Company, the Underwriters and their respective affiliates that (i) the decision to acquire
or accept this Certificate or an interest herein has been made by a duly authorized fiduciary of the Benefit Plan Investor that (A) is independent (as that term is used in 29 C.F.R. 2510.3-21(c)(1)) of
the Company, each of the Underwriters, and their respective affiliates; (B) is a bank, an insurance carrier, a registered investment adviser, a registered broker-dealer, or an independent fiduciary that holds, or has under management or
control, total assets of at least $50 million (in each case, as specified in 29 C.F.R. 2510.3-21(c)(1)(i)(A)-(E)); (C) is capable of evaluating investment risks independently, both in general and with
regard to particular transactions and investment strategies (including, without limitation, with respect to the decision to acquire or accept this Certificate or an interest herein); (D) has been fairly informed that the Company, the Underwriters,
and their respective affiliates have not and will not undertake to provide impartial investment advice, or to give advice in a fiduciary capacity, in connection with the acquisition or acceptance of this Certificate or an interest herein;
(E) has been fairly informed of the existence and nature of the financial interests that the Company, the Underwriters, and their respective affiliates have in the Benefit Plan Investor’s acquisition or acceptance of this Certificate or an
interest herein, which interests may conflict with the interest of the Benefit Plan Investor, as more fully described in the offering materials; and (F) is a fiduciary under ERISA or the Code, or both, with respect to the decision to acquire or
accept this Certificate or an interest herein and is responsible for exercising (and has exercised) independent judgment in evaluating whether to invest the assets of such Benefit Plan Investor in this Certificate or an interest herein; and
(ii) neither the Benefit Plan Investor nor such duly authorized fiduciary of the Benefit Plan Investor is paying the Company, any Underwriter, or any of their respective affiliates, any fee or other compensation directly for the provision of
investment advice (as opposed to other services) in connection with the Benefit Plan Investor’s acquisition or acceptance of this Certificate or an interest herein. 

THE AGREEMENT AND, UNTIL THE TRANSFER, THIS CERTIFICATE SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF
DELAWARE AND THE OBLIGATIONS, RIGHTS AND REMEDIES OF THE PARTIES HEREUNDER SHALL BE DETERMINED IN ACCORDANCE WITH SUCH LAWS. THE RELATED PASS THROUGH TRUST AGREEMENT AND, FROM AND AFTER THE TRANSFER, THIS CERTIFICATE SHALL BE GOVERNED AND CONSTRUED
IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK AND THE OBLIGATIONS, RIGHTS AND REMEDIES OF THE PARTIES HEREUNDER SHALL BE DETERMINED IN ACCORDANCE WITH SUCH LAWS. 

  
 A-5 







 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. 

  
 A-6 







 IN WITNESS WHEREOF, the Trustee has caused this Certificate to be duly executed. 

 

			
	UNITED AIRLINES PASS THROUGH TRUST 2018-1B-O
		
	By:	 	WILMINGTON TRUST, NATIONAL ASSOCIATION,
		 	as Trustee
		
	By:	 	  

		 	Name:
		 	Title:



  
 A-7 







 FORM OF THE TRUSTEE’S CERTIFICATE OF AUTHENTICATION 

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

 

			
	 WILMINGTON TRUST, NATIONAL ASSOCIATION,

as Trustee



 
			
		
	By:	 	  



 
			
		 	Name:
		 	Title:








 EXHIBIT B 

The Depositary Trust Company 
 A
subsidiary of the Depository Trust & Clearing Corporation 
 ISSUER LETTER OF REPRESENTATIONS 

(To be completed by Issuer and Co-lssuer(s), if applicable) 

United Airlines Pass Through Trust 2018-1 B 

(Name of Issuer and Co-lssuer(s), if applicable) 

4.600% United Airlines Pass Through Certificates, Series 2018-1 B 

(Security Description, including series designation if applicable) 

90932N AA1 
 (CUSIP
Number(s) of the Securities) 
 May 9, 2018 

(Date)       
 The
Depository Trust 
 Company 18301 Bermuda 
 Green Drive Tampa,
FL 
 33647 
 Attention: Underwriting 

Department 
 Ladies and Gentlemen: 

This letter sets forth our understanding with respect to the Securities represented by the CUSIP number(s) referenced above (the
“Securities”). Issuer requests that The Depository Trust Company (“DTC”) accept the Securities as eligible for deposit at DTC. 

Issuer is: (Note: Issuer must represent one and cross out the other ) [incorporated] [formed under the laws of]
___Delaware____________ The DTC Clearing Participant Credit Suisse Securities (USA) LLC will distribute the Securities through DTC. 

To induce DTC to accept the Securities as eligible for deposit at DTC, and to act in accordance with DTC’s Rules with respect to the
Securities, Issuer represents to DTC that Issuer will comply with the requirements stated in DTC’s Operational Arrangements, as they may be amended from time to time. 






 Note: 

Schedule A contains statements that DTC believes accurately describe DTC, the method of effecting book-entry transfers of securities
distributed through DTC, and certain related matters. 
  

	
	Very truly yours,
	
	United Airlines Pass Through Trust 2018-1B
	








 EXHIBIT C 

FORM OF ASSIGNMENT AND ASSUMPTION AGREEMENT 

United Airlines Pass Through Trust 2018-1B-O 

ASSIGNMENT AND ASSUMPTION AGREEMENT (2018-1B-O), dated
                    ,              (the “Assignment
Agreement”), between Wilmington Trust, National Association, a national banking association (“WTNA”), not in its individual capacity except as expressly provided herein, but solely as trustee under the Pass Through Trust
Agreement dated as of October 3, 2012 (as amended or modified from time to time, the “Basic Agreement”), as supplemented by the Trust Supplement No.
2018-1B-O dated as of May 23, 2018 (the “Trust Supplement” and together with the Basic Agreement, the “Agreement”) in respect of
the United Airlines Pass Through Trust 2018-1B-O (the “Assignor”), and Wilmington Trust, National Association, a national banking association, not in
its individual capacity except as expressly provided herein, but solely as trustee under the Basic Agreement as supplemented by the Trust Supplement No. 2018-1B-S dated
as of May 23, 2018 (the “New Supplement”, and, together with the Basic Agreement, the “New Agreement”) in respect of the United Airlines Pass Through Trust 2018-1B-S (the “Assignee”). 
 W I T N E S S E T H: 

WHEREAS, the parties hereto desire to effect on the date hereof (the “Transfer Date”) (a) the transfer by the
Assignor to the Assignee of all of the right, title and interest of the Assignor in, under and with respect to, among other things, the Trust Property and each of the documents listed in Schedule I hereto (the “Scheduled Documents”)
and (b) the assumption by the Assignee of the obligations of the Assignor (i) under the Scheduled Documents and (ii) in respect of the Applicable Certificates issued under the Agreement; and 

WHEREAS, the Scheduled Documents permit such transfer upon satisfaction of certain conditions heretofore or concurrently herewith being
complied with; 
 NOW, THEREFORE, in consideration of the premises and of the mutual covenants and agreements herein contained, the parties
hereto do hereby agree as follows (capitalized terms used herein without definition having the meaning ascribed thereto in the Agreement): 

1. Assignment. The Assignor does hereby sell, assign, convey, transfer and set over unto the Assignee as of the Transfer Date all of its
present and future right, title and interest in, under and with respect to the Trust Property and the Scheduled Documents and each other contract, agreement, document or instrument relating to the Trust Property or the Scheduled Documents (such
other contracts, agreements, documents or instruments, together with the Scheduled Documents, to be referred to as the “Assigned Documents”), and any proceeds therefrom, together with all documents and instruments evidencing any of
such right, title and interest. 

  
 C-1 







 2. Assumption. The Assignee hereby assumes for the benefit of the Assignor and each of the
parties listed in Schedule II hereto (collectively, the “Beneficiaries”) all of the duties and obligations of the Assignor, whenever accrued, pursuant to the Assigned Documents and hereby confirms that it shall be deemed a party to
each of the Assigned Documents to which the Assignor is a party and shall be bound by all the terms thereof (including the agreements and obligations of the Assignor set forth therein) as if therein named as the Assignor. Further, the Assignee
hereby assumes for the benefit of the Assignor and the Beneficiaries all of the duties and obligations of the Assignor under the Outstanding Applicable Certificates and hereby confirms that the Applicable Certificates representing Fractional
Undivided Interests under the Agreement shall be deemed for all purposes of the Agreement and the New Agreement to be certificates representing the same fractional undivided interests under the New Agreement equal to their respective beneficial
interests in the trust created under the Agreement. 
 3. Effectiveness. This Assignment Agreement shall be effective upon the execution and
delivery hereof by the parties hereto, and each Applicable Certificateholder, by its acceptance of its Applicable Certificate or a beneficial interest therein, agrees to be bound by the terms of this Assignment Agreement. 

4. Payments. The Assignor hereby covenants and agrees to pay over to the Assignee, if and when received following the Transfer Date, any
amounts (including any sums payable as interest in respect thereof) paid to or for the benefit of the Assignor that, under Section 1 hereof, belong to the Assignee. 

5. Further Assurances. The Assignor shall, at any time and from time to time, upon the request of the Assignee, promptly and duly
execute and deliver any and all such further instruments and documents and take such further action as the Assignee may reasonably request to obtain the full benefits of this Assignment Agreement and of the rights and powers herein granted. The
Assignor agrees to deliver any Applicable Certificates, and all Trust Property, if any, then in the physical possession of the Assignor, to the Assignee. 

6. Representations and Warranties. (a) The Assignee represents and warrants to the Assignor and each of the Beneficiaries that:

 (i) it has all requisite power and authority and legal right to enter into and carry out the transactions contemplated
hereby and to carry out and perform the obligations of the “Pass Through Trustee” under the Assigned Documents; 

(ii) on and as of the date hereof, the representations and warranties of the Assignee set forth in Section 7.15 of the
Basic Agreement and Section 5.04 of the New Supplement are true and correct. 
 (b) The Assignor represents and warrants to the Assignee
that: 
 (i) it is duly incorporated, validly existing and in good standing under the laws of the United States and has the
full trust power, authority and legal right under the laws of the United States and of the state of the United States in which it is located pertaining to its trust and fiduciary powers to execute and deliver this Assignment Agreement; 

  
 C-2 







 (ii) the execution and delivery by it of this Assignment Agreement and the
performance by it of its obligations hereunder have been duly authorized by it and will not violate its articles of association or by-laws or the provisions of any indenture, mortgage, contract or other
agreement to which it is a party or by which it is bound; and 
 (iii) this Assignment Agreement constitutes the legal, valid
and binding obligations of it enforceable against it in accordance with its terms, except as the same may be limited by applicable bankruptcy, insolvency, reorganization, moratorium or similar laws affecting the rights of creditors generally and by
general principles of equity, whether considered in a proceeding at law or in equity. 
 7. GOVERNING LAW. THIS ASSIGNMENT
AGREEMENT SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK INCLUDING MATTERS OF CONSTRUCTION, VALIDITY AND PERFORMANCE. 

8. Counterparts. This Assignment Agreement may be executed in any number of counterparts, all of which together shall constitute a
single instrument. It shall not be necessary that any counterpart be signed by both parties so long as each party shall sign at least one counterpart. 

9. Third Party Beneficiaries. The Assignee hereby agrees, for the benefit of the Beneficiaries, that its representations, warranties and
covenants contained herein are also intended to be for the benefit of each Beneficiary, and each Beneficiary shall be deemed to be an express third party beneficiary with respect thereto, entitled to enforce directly and in its own name any rights
or claims it may have against such party as such beneficiary. 
 10. Notice. Promptly following the Transfer Date, the Assignee shall
notify the Depositary of the occurrence of the assignment hereunder and the name and contact information of the Assignee. 

  
 C-3 







 IN WITNESS WHEREOF, the parties hereto, through their respective officers thereunto duly
authorized, have duly executed this Assignment Agreement as of the day and year first above written. 
  

			
	ASSIGNOR:
		
		 	WILMINGTON TRUST, NATIONAL ASSOCIATION, not in its individual capacity except as expressly provided herein, but solely as trustee under the Pass Through Trust Agreement and Trust Supplement in respect of the United Airlines Pass
Through Trust 2018-1B-O
		
	By:	 	  

		 	Name:
		 	Title:
	
	ASSIGNEE:
		
		 	WILMINGTON TRUST, NATIONAL ASSOCIATION, not in its individual capacity except as expressly provided herein, but solely as trustee under the Pass Through Trust Agreement and Trust Supplement in respect of the United Airlines Pass
Through Trust 2018-1B-S
		
	By:	 	  

		 	Name:
		 	Title:



  
 C-4 







 Schedule I 

Schedule of Assigned Documents 

(1) Amended and Restated Intercreditor Agreement dated as of May 23, 2018 among the Trustee, the Other Trustees party thereto, the
Liquidity Provider, the liquidity provider relating to the Class AA Certificates, the liquidity provider relating to the Class A Certificates and the Subordination Agent. 

(2) Escrow and Paying Agent Agreement (Class B) dated as of May 23, 2018 among the Escrow Agent, the Underwriters, the Trustee and the
Escrow Paying Agent. 
 (3) Note Purchase Agreement dated as of February 14, 2018 (as amended by Amendment No. 1 to the Note
Purchase Agreement dated as of May 23) among the Company, the Trustee, the Other Trustees party thereto, the Subordination Agent, the Escrow Agent, and the Escrow Paying Agent, the escrow agent relating to the Class AA Certificates, the escrow
agent relating to the Class A Certificates, the escrow paying agent relating to the Class AA Certificates and the escrow paying agent relating to the Class A Certificates. 

(4) Deposit Agreement (Class B) dated as of May 23, 2018 between the Escrow Agent and the Depositary. 

(5) Each of the Operative Agreements (as defined in the Participation Agreement for each Aircraft) in effect as of the Transfer Date. 






 Schedule II 

Schedule of Beneficiaries 
 Wilmington Trust,
National Association, not in its individual capacity but solely as Subordination Agent 
 Wilmington Trust, National Association, not in its individual
capacity but solely as Escrow Paying Agent 
 National Australia Bank Limited, acting through its New York Branch, as Liquidity Provider 

Citibank, N.A., as Depositary 
 United Airlines, Inc. 

Credit Suisse Securities (USA) LLC, as Underwriter 
 Citigroup
Global Markets Inc., as Underwriter 
 Goldman Sachs & Co. LLC, as Underwriter 

Deutsche Bank Securities Inc., as Underwriter 
 Morgan
Stanley & Co. LLC, as Underwriter 
 Barclays Capital Inc., as Underwriter 

Merrill Lynch, Pierce, Fenner & Smith Incorporated, as Underwriter 

BNP Paribas Securities Corp., as Underwriter 
 Credit Agricole
Securities (USA) Inc., as Underwriter 
 J.P. Morgan Securities LLC, as Underwriter 

Standard Chartered Bank, as Underwriter 
 Wells Fargo Securities,
LLC, as Underwriter 
 U.S. Bank National Association, as Escrow Agent 

Each of the other parties to the Assigned Documents 

  
 C-2