Exhibit 10.23

6-1162-IRS-0182

United Air Lines, Inc.

P. O. Box 66100

Chicago, IL 60601



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|Subject:   |  | Priviledged and Confidential Matters                                                                                                                                  
|           | 
|Reference: |  | Purchase Agreement No. 3427 (Purchase Agreement) between The Boeing Company (Boeing) and United Air Lines, Inc. (Customer) relating to Model 787-8 aircraft (Aircraft)

This letter agreement (Letter Agreement) amends and supplements the Purchase Agreement. All terms used but not
defined in this Letter Agreement have the same meaning as in the Purchase Agreement.

Boeing and Customer agree that certain
commercial and financial information contained in or transmitted pursuant to the Purchase Agreement and the Aircraft General Terms Agreement (AGTA) (together the Purchase Agreement) between Boeing and Customer and all letter agreements
made a part of the Purchase Agreement, including exhibits or attachments thereto are considered by Boeing and Customer as privileged and confidential and the parties agree that the information contained therein or transmitted pursuant to
(Information) represents confidential business information. Except as specified below, each of Boeing and Customer is prohibited from disclosing the Information to any person, entity, or government agency. Each party shall protect the
confidentiality of such Information in the manner similar to how a party protects its own Information of a similar nature, but with no less than a reasonable standard of care. This provision shall not restrict a party from taking any steps necessary
to protect and safeguard its interests relating to the Information, including obtaining a protective order or other injunctive relief, where appropriate.



| | (a) | Employees. A party may disclose the Information to its own employees who (i) have a need to know the Information for purposes of assisting said party in the
evaluation or administration of the Purchase Agreement or such partys business operations and (ii) have been instructed to not disclose the Information except as provided by this Letter Agreement.
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| | (b) | Professional Advisors. A party may disclose the Information to its auditors, insurers, financial advisors, consultants and attorneys
(Professional Advisors) who have a need to know the
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P.A. No. 3427

Priviledged and Confidential Matters

BOEING / UNITED PROPRIETARY



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United Air Lines, Inc.

6-1162-IRS-0182



| | Information in connection with providing services to said party only when said party has first obtained from the Professional Advisor a written obligation of confidentiality and restricted use
that is no less restrictive than the terms of this Letter Agreement. Each party shall be fully responsible to the other party for the Professional Advisors compliance with such obligations.
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| | (c) | Regulatory Requirements. A party may disclose in a regulatory or other government filing that part of the Information which is required by applicable law or
regulation to be disclosed in such regulatory or other governmental filings, including filings with the Securities and Exchange Commission (SEC), but only in accordance with the following requirements:
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| | (i) | The disclosing party shall advise the other party in writing of such disclosure requirement prior to making such disclosure to enable the other party to take those
steps it deems necessary to protect the Information; and
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| | (ii) | The disclosing party shall, as requested by the other party, seek redaction and/or confidential treatment for the Information or parts thereof from the SEC or other
applicable regulators.
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P.A. No. 3427

Priviledged and Confidential Matters

BOEING / UNITED PROPRIETARY



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United Air Lines, Inc.

6-1162-IRS-0182



|                            |  |                 
|--------------------------- |  | ----------------
|Very truly yours,          
|                           
|THE BOEING COMPANY         
|                            | 
|By                          |  | /s/ Nobuko Wiles
|                            | 
|Its                         |  | Attorney-In-Fact
|                           
|ACCEPTED AND AGREED TO this
|                           
|Date: February 19, 2010    
|                           
|UNITED AIR LINES, INC.     

|    |  |                                                     
|--- |  | ----------------------------------------------------
|    | 
|By  |  | /s/ Kathryn A. Mikells                              
|    | 
|Its |  | Executive Vice President and Chief Financial Officer



P.A. No. 3427

Priviledged and Confidential Matters

BOEING / UNITED PROPRIETARY