NOTE PURCHASE AGREEMENT

Exhibit 4.5

NOTE PURCHASE AGREEMENT

Dated as of October 13, 2009

Among

UNITED AIR LINES, INC.,

WILMINGTON TRUST COMPANY,

as Pass Through Trustee under the

Pass Through Trust Agreement

WILMINGTON TRUST COMPANY,

as Escrow Agent

WILMINGTON TRUST COMPANY,

as Paying Agent

and

WILMINGTON TRUST COMPANY,

as Subordination Agent

Vedder Price P.C.

Chicago, Illinois

TABLE OF CONTENTS

i

NOTE PURCHASE AGREEMENT

This NOTE PURCHASE AGREEMENT , dated as of October 13, 2009 (this “ Agreement ”), among (i)  UNITED AIR LINES, INC. , a Delaware corporation (the “ Company ”), (ii)  WILMINGTON TRUST COMPANY (“ WTC ”), a Delaware banking corporation, not in its individual capacity except as otherwise expressly provided herein, but solely as trustee (in such capacity together with its successors in such capacity, the “ Pass Through Trustee ”) under the Pass Through Trust Agreement (as defined below), (iii)  WILMINGTON TRUST COMPANY , a Delaware banking corporation, as subordination agent and trustee (in such capacity together with its successors in such capacity, the “ Subordination Agent ”) under the Intercreditor Agreement (as defined below), (iv)  WILMINGTON TRUST COMPANY , a national banking association, as Escrow Agent (in such capacity together with its successors in such capacity, the “ Escrow Agent ”), under the Escrow and Paying Agent Agreement (as defined below) and (v)  WILMINGTON TRUST COMPANY , a Delaware banking corporation, as Paying Agent (in such capacity together with its successors in such capacity, the “ Paying Agent ”) under the Escrow and Paying Agent Agreement.

W I T N E S S E T H :

WHEREAS , capitalized terms used but not defined herein shall have the meanings ascribed to such terms in Annex A hereto;

WHEREAS , the Company is the owner of (i) two (2) unencumbered Boeing 767-300ER aircraft as further identified on Schedule I hereto (the “ Unencumbered Aircraft ”) and (ii) ten (10) Airbus A319-131 aircraft, six (6) Airbus A320-232 aircraft, five (5) Boeing 767-300ER aircraft, three (3) Boeing 777-200ER aircraft and five (5) Boeing 747-400 aircraft as further identified on Schedule I hereto, each of which is subject to an existing securing interest (the “ Encumbered Aircraft ” and together with the Unencumbered Aircraft, collectively, the “ Aircraft ”);

WHEREAS , pursuant to this Agreement, the company wishes to refinance Aircraft prior to the Cut-Off Date;

WHEREAS , pursuant to the Pass Through Trust Supplement identified on Schedule II hereto (the “ Trust Supplement ”; and together with the Basic Pass Through Trust Agreement, the “ Pass Through Trust Agreement ”), on the Issuance Date, a grantor trust (the “ Pass Through Trust ”) will be created to facilitate certain of the transactions contemplated hereby, including, without limitation, the issuance and sale of enhanced pass through certificates pursuant thereto (collectively, the “ Certificates ”) to provide the refinancing of the Aircraft;

WHEREAS , concurrently with the execution and delivery of this Agreement, (i) the Escrow Agent and the Depositary have entered into the Deposit Agreement, dated as of the Issuance Date, relating to the Pass Through Trust (the “ Deposit Agreement ”) whereby the Escrow Agent agreed to direct the Underwriters to make certain deposits referred to therein on the Issuance Date (the “ Initial Deposits ”) and to permit the Pass Through Trustee to make additional deposits from time to time thereafter (the Initial Deposits together with

[Note Purchase Agreement]

such additional deposits are collectively referred to as the “ Deposits ”) and (ii) the Pass Through Trustee, Underwriters, Paying Agent and Escrow Agent have entered into the Escrow and Paying Agent Agreement, dated as of the Issuance Date, relating to the Pass Through Trust (the “ Escrow and Paying Agent Agreement ”), whereby, among other things, (a) the Underwriters agreed, on and subject to the terms and conditions specified therein, to deliver an amount equal to the amount of the Initial Deposits to the Depositary on behalf of the Escrow Agent and (b) the Escrow Agent, upon the Depositary receiving such amount, agreed to deliver escrow receipts to be affixed to each Certificate;

WHEREAS , upon receipt of a Closing Notice with respect to an Aircraft, subject to the terms and conditions of this Agreement, the Pass Through Trustee will enter into the applicable Financing Agreements relating to such Aircraft;

WHEREAS , upon the refinancing of an Aircraft, the Pass Through Trustee will fund its purchase of Equipment Notes with the proceeds of the Deposits withdrawn by the Escrow Agent under the Deposit Agreement;

WHEREAS , UAL Corporation, a Delaware corporation (“ UAL ”), will guarantee the payment obligations of the Company under the Indentures, the Participation Agreements and the Equipment Notes pursuant to a guarantee dated as of the date hereof (the “ UAL Guarantee ”);

WHEREAS , concurrently with the execution and delivery of this Agreement, (i) Morgan Stanley Bank, N.A., a national banking association organized and existing under the laws of the United States (the “ Liquidity Provider ”) entered into a revolving credit agreement (the “ Liquidity Facility ”), for the benefit of the Certificateholders of the Pass Through Trust, with the Subordination Agent, as agent and trustee for the Pass Through Trustee on behalf of the Pass Through Trust; and (ii) the Pass Through Trustee, the Liquidity Provider and the Subordination Agent have entered into the Intercreditor Agreement, dated as of the date hereof (the “ Intercreditor Agreement ”); and

WHEREAS , the Company has entered into the Underwriting Agreement dated October 5 2009 (the “ Underwriting Agreement ”) with the several Underwriters (the “ Underwriters ”) named therein, which provides that the Company will cause the Pass Through Trustee to issue and sell the Certificates to the Underwriters.

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

Section 1.       Financing of Aircraft . (a) The Company agrees to finance the Aircraft in the manner provided herein, all on and subject to the terms and conditions hereof and of the relevant Financing Agreements.

  (b)      In furtherance of the foregoing, the Company agrees to give the parties hereto, the Depositary and each of the Rating Agencies not less than two Business Days’ prior notice substantially in the

2

[Note Purchase Agreement]

form of Exhibit A hereto (a “ Closing Notice ”) of the scheduled closing date (the “ Scheduled Closing Date ”) (or, in the case of a substitute Closing Notice under Section 1(e) hereof, one Business Days’ prior notice) in respect of the financing of the Aircraft under this Agreement, which notice shall:

    (i)      specify the Scheduled Closing Date of the Aircraft (which shall be a Business Day before the Cut-off Date and the date (the “ Funding Date ”) on which the financing therefor in the manner provided herein shall be consummated);

    (ii)      instruct the Pass Through Trustee to enter into the Participation Agreements included in the Financing Agreements with respect to each relevant Aircraft at such a time on or before the Funding Date specified in such Closing Notice and to perform its obligations thereunder;

    (iii)      instruct the Pass Through Trustee to instruct the Escrow Agent to provide a Notice of Purchase Withdrawal to the Depositary with respect to the Equipment Notes to be issued to the Pass Through Trustee in connection with the financing of the relevant Aircraft; and

    (iv)      specify the aggregate principal amount of the Equipment Notes to be issued, and purchased by the Pass Through Trustee, in connection with the financing of the Aircraft scheduled on such Funding Date.

  (c)     Upon receipt of a Closing Notice, the Pass Through Trustee shall, and shall cause the Subordination Agent to, enter into and perform their respective obligations under the Participation Agreements specified in such Closing Notice, provided that such Participation Agreements and the Indentures to be entered into pursuant to such Participation Agreements shall be in the forms thereof annexed hereto. With respect to each Aircraft to be refinanced on a Closing Date, the Company shall cause WTC (or such other person that meets the eligibility requirements to act as loan trustee under the relevant Indentures) to execute as Loan Trustee the Financing Agreements relating to such Aircraft to which such Loan Trustee is intended to be a party, and the Company shall concurrently therewith execute such Financing Agreements to which the Company is intended to be a party and perform its respective obligations thereunder. Upon the request of either Rating Agency, the Company shall deliver or cause to be delivered to such Rating Agency a true and complete copy of each Financing Agreement relating to the financing of each Aircraft together with a true and complete set of the closing documentation (including legal opinions) delivered to the related Loan Trustee, Subordination Agent and Pass Through Trustee under the related Participation Agreement.

  (d)     The Company agrees that all Equipment Notes issued pursuant to any Indenture shall initially be registered in the name of the Subordination Agent on behalf of the Pass Through Trustee (or, in the case of any Additional Series Equipment Notes, on behalf of the Additional Pass Through Trustee with respect to the corresponding Additional Certificates).

  (e)     If after giving any Closing Notice, there shall be a delay in the refinancing of the Encumbered Aircraft, or if on the Scheduled Closing Date of the Encumbered Aircraft or Unencumbered

3

[Note Purchase Agreement]

Aircraft referred to therein the financing thereof in the manner contemplated hereby shall not be consummated for whatever reason, the Company shall give the parties hereto and the Depositary prompt notice thereof. Concurrently with the giving of such notice of postponement or subsequently, the Company shall give the parties hereto and the Depositary a substitute Closing Notice specifying the date to which the financing of such Aircraft shall have been re-scheduled (which shall be a Business Day before the Cut-off Date on which the Escrow Agent shall be entitled to withdraw one or more Deposits under the Deposit Agreement to enable the Pass Through Trustee to fund its purchase of the Equipment Notes). Upon receipt of any such notice of postponement, the Pass Through Trustee shall comply with its obligations under Section 5.01 of the Trust Supplement and thereafter the financing of such Aircraft, as specified in such substitute Closing Notice, shall take place on the re-scheduled Closing Date therefor (all on and subject to the terms and conditions of the relevant Financing Agreements) unless further postponed as provided herein.

  (f)      The Company shall have no liability for the failure of the Pass Through Trustee to purchase Equipment Notes with respect to any Aircraft it is obligated to purchase hereunder.

  (g)      Anything herein to the contrary notwithstanding, the Company shall not have the right, and shall not be entitled, at any time to request the issuance of Equipment Notes to the Pass Through Trustee in an aggregate principal amount in excess of the amount of the Deposits then available for withdrawal by the Escrow Agent under and in accordance with the provisions of the Deposit Agreement.

Section 2.       Conditions Precedent . The obligation of the Pass Through Trustee to enter into, and to cause the Subordination Agent to enter into, any Participation Agreement as directed pursuant to a Closing Notice and to perform its obligations thereunder is subject to no Triggering Event having occurred. Anything herein to the contrary notwithstanding, the obligation of the Pass Through Trustee to purchase Equipment Notes shall terminate on the Cut-off Date.

Section 3.       Representations and Warranties . (a) The Company represents and warrants that:

    (i)      the Company is duly incorporated, validly existing and in good standing under the laws of the State of Delaware and is a “citizen of the United States” as defined in Section 40102(a)(15) of the Act, and has the full corporate power, authority and legal right under the laws of the State of Delaware to execute and deliver this Agreement and each Financing Agreement to which it will be a party and to carry out the obligations of the Company under this Agreement and each Financing Agreement to which it will be a party;

    (ii)      the execution and delivery by the Company of this Agreement and the performance by the Company of its obligations under this Agreement have been duly authorized by the Company and will not violate its Restated Certificate of Incorporation or by-laws or (other than any violation that would

4

[Note Purchase Agreement]

not result in a Material Adverse Change to the Company) the provisions of any indenture, mortgage, contract or other agreement to which it is a party or by which it is bound; and

    (iii)      assuming the due authorization, execution and delivery hereof by the other parties hereto, this Agreement constitutes the legal, valid and binding obligation of the Company, 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.

(b)      WTC represents and warrants that:

    (i)      WTC is duly incorporated, validly existing and in good standing under the laws of the State of Delaware and is a “citizen of the United States” as defined in Section 40102(a)(15) of the Act, and has the full corporate power, authority and legal right under the laws of the State of Delaware and the United States pertaining to its banking, trust and fiduciary powers to execute and deliver this Agreement and each Financing Agreement to which it will be a party and to carry out the obligations of WTC, in its capacity as Subordination Agent, Paying Agent, Escrow Agent or Pass Through Trustee, as the case may be, under this Agreement and each Financing Agreement to which it will be a party;

    (ii)      the execution and delivery by WTC, in its capacity as Subordination Agent, Paying Agent, Escrow Agent or Pass Through Trustee, as the case may be, of this Agreement and the performance by WTC, in its capacity as Subordination Agent, Paying Agent, Escrow Agent or Pass Through Trustee, as the case may be, of its obligations under this Agreement have been duly authorized by WTC, in its capacity as Subordination Agent, Paying Agent, Escrow Agent or Pass Through Trustee, as the case may be, 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 Agreement constitutes the legal, valid and binding obligations of WTC, in its capacity as Subordination Agent, Paying Agent, Escrow Agent or Pass Through Trustee, as the case may be, 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.

(c)      The Pass Through Trustee hereby confirms to each of the other parties hereto that its representations and warranties set forth in Section 7.15 of the Basic Pass Through Trust Agreement and Section 4.03 of the Trust Supplement are true and correct as of the date hereof.

5

[Note Purchase Agreement]

(d)      The Subordination Agent represents and warrants that:

    (i)      the Subordination Agent is duly incorporated, validly existing and in good standing under the laws of the State of Delaware, and has the full corporate power, authority and legal right under the laws of the State of Delaware and the United States pertaining to its banking, trust and fiduciary powers to execute and deliver this Agreement and each Financing Agreement to which it is or will be a party and to perform its obligations under this Agreement and each Financing Agreement to which it is or will be a party;

    (ii)      this Agreement has been duly authorized, executed and delivered by the Subordination Agent; this Agreement constitutes the legal, valid and binding obligations of the Subordination Agent 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;

    (iii)      none of the execution, delivery and performance by the Subordination Agent of this Agreement contravenes any law, rule or regulation of the State of Delaware or any United States governmental authority or agency regulating the Subordination Agent’s banking, trust or fiduciary powers or any judgment or order applicable to or binding on the Subordination Agent and do not contravene the Subordination Agent’s articles of association or by-laws or result in any breach of, or constitute a default under, any agreement or instrument to which the Subordination Agent is a party or by which it or any of its properties may be bound;

    (iv)      neither the execution and delivery by the Subordination Agent of this Agreement nor the consummation by the Subordination Agent of any of the transactions contemplated hereby requires the consent or approval of, the giving of notice to, the registration with, or the taking of any other action with respect to, any Delaware governmental authority or agency or any federal governmental authority or agency regulating the Subordination Agent’s banking, trust or fiduciary powers;

    (v)      there are no Taxes payable by the Subordination Agent imposed by the State of Delaware or any political subdivision or taxing authority thereof in connection with the execution, delivery and performance by the Subordination Agent of this Agreement (other than franchise or other taxes based on or measured by any fees or compensation received by the Subordination Agent for services rendered in connection with the transactions contemplated by the Intercreditor Agreement or the Liquidity Facility), and there are no Taxes payable by the Subordination Agent imposed by the State of Delaware or any political subdivision thereof in connection with the acquisition, possession or ownership by the Subordination Agent of any of the Equipment Notes (other than franchise or other taxes based on or measured by any fees or compensation received by the Subordination Agent for services rendered in connection with the transactions contemplated by the Intercreditor Agreement or the Liquidity Facility); and

6

[Note Purchase Agreement]

    (vi)      there are no pending or threatened actions or proceedings against the Subordination Agent before any court or administrative agency which individually or in the aggregate, if determined adversely to it, would materially adversely affect the ability of the Subordination Agent to perform its obligations under this Agreement.

(e)      The Escrow Agent represents and warrants that:

    (i)      the Escrow Agent is duly incorporated, validly existing and in good standing under the laws of the State of Delaware and has the full corporate power, authority and legal right under the laws of the State of Delaware pertaining to its banking, trust and fiduciary powers to execute and deliver this Agreement, the Deposit Agreement and the Escrow and Paying Agent Agreement (collectively, the “ Escrow Agent Agreements ”) and to carry out the obligations of the Escrow Agent under each of the Escrow Agent Agreements;

    (ii)      the execution and delivery by the Escrow Agent of each of the Escrow Agent Agreements and the performance by the Escrow Agent of its obligations hereunder and thereunder have been duly authorized by the Escrow Agent 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)      each of the Escrow Agent Agreements constitutes the legal, valid and binding obligations of the Escrow Agent 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.

(f)      The Paying Agent represents and warrants that:

    (i)      the Paying Agent is duly incorporated, validly existing and in good standing under the laws of the State of Delaware and has the full corporate power, authority and legal right under the laws of the State of Delaware and the United States pertaining to its banking, trust and fiduciary powers to execute and deliver this Agreement and the Escrow and Paying Agent Agreement (collectively, the “ Paying Agent Agreements ”) and to carry out the obligations of the Paying Agent under each of the Paying Agent Agreements;

    (ii)      the execution and delivery by the Paying Agent of each of the Paying Agent Agreements and the performance by the Paying Agent of its obligations hereunder and thereunder have been duly authorized by the Paying Agent 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)      each of the Paying Agent Agreements constitutes the legal, valid and binding obligations of the Paying Agent 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

[Note Purchase Agreement]

Section 4.       Covenants . (a) The Company covenants with each of the other parties hereto that:

    (i)      the Company shall not issue any Additional Series Equipment Notes pursuant to any Indenture, unless it shall have obtained a Rating Agency Confirmation from each Rating Agency. Any issuance of Additional Series Equipment Notes shall be subject to the terms of the Indentures and Section 9.1(c) of the Intercreditor Agreement.

    (ii)      the Company agrees to provide written notice to each of the parties hereto of the occurrence of the Cut-off Date no later than one Business Day after the date thereof, such notice to refer specifically to the Pass Through Trustee’s obligation to assign, transfer and deliver all of its right, title and interest to the Trust Property (as defined in the Pass Through Trust Agreement) to the trustee of the Related Trust (as defined in the Pass Through Trust Agreement) in accordance with Section 7.01 of the Trust Supplement;

    (iii)      If (x) the Depositary’s short-term unsecured debt rating or short-term issuer credit rating, as the case may be, shall at any time fall below A-1+ from Standard & Poor’s Ratings Services or P-1 from Moody’s Investors Service, Inc. (such minimum ratings, the “ Depositary Threshold Ratings ”) or (y) the Company or the Depositary, in its sole discretion, gives written notice to the other of its election that the Depositary be replaced, the Company shall, within 45 days after such event occurring, cause the Depositary to be replaced with a depositary bank (a “ Replacement Depositary ”) on the following terms and preconditions:

  (A)      the Replacement Depositary must meet the Depositary Threshold Ratings and the Company shall have obtained written confirmation from each Rating Agency that such replacement will not cause a reduction of the rating then in effect for the Certificates by such Rating Agency (without regard to any downgrading of any rating of the Depositary being replaced);

  (B)      the Company shall pay all fees, expenses and other amounts then owing to the replaced Depositary and, except as expressly provided in clause (C) below, the Company shall pay any up-front fee of the Replacement Depositary and (without limitation of the foregoing) all out-of-pocket expenses (including reasonable fees and expenses of legal counsel) of the parties hereto (including without limitation all amounts payable to the Rating Agencies) incurred in connection with such replacement;

  (C)      solely in the case of the Depositary making an election in its discretion that it be replaced (and without limitation of clause (A) above), (x) the notice given by the Depositary to the Company shall nominate a Replacement Depositary, which shall satisfy all of terms and

8

[Note Purchase Agreement]

preconditions of this Section 4(a)(iii) (and the Company shall have the right to utilize such nominee as the Replacement Depositary or to select another Replacement Depositary), (y) the fees, expenses, indemnities and other amounts payable to the Replacement Depositary upon its execution of the Replacement Deposit Agreement or thereafter shall not to any extent exceed those which would have been payable to the Depositary had such replacement not occurred (it being specifically understood and agreed that any up-front fee of the Replacement Depositary shall be paid by the replaced Depositary, provided that, if the Company selects a Replacement Depositary other than the nominee of the replaced Depositary and the upfront fee of such selection exceeds that of such nominee, the Company shall pay such excess), and (without limitation of the foregoing) the Depositary shall pay all out-of-pocket expenses (including reasonable fees and expenses of legal counsel) of the parties hereto (including without limitation all amounts payable to the Rating Agencies) incurred in connection with such replacement, and (z) the Replacement Depositary shall be willing to enter into a Replac