Exhibit 10.4

Supplemental Agreement No. 39

to

Purchase Agreement No. 1977

between

The Boeing Company

and

American Airlines, Inc.

Relating to Boeing Model 737-800 Aircraft

THIS SUPPLEMENTAL AGREEMENT No. 39 (SA-39), entered into as of June 2, 2016, by and between THE BOEING COMPANY, a Delaware corporation
with offices in Seattle, Washington (Boeing), and AMERICAN AIRLINES, INC., a Delaware corporation with offices in Fort Worth, Texas, together with its successors and permitted assigns (Customer);

WHEREAS, Boeing and Customer entered into Purchase Agreement No. 1977 dated October 31, 1997, relating to Boeing Model 737-823 aircraft,
as amended and supplemented (Purchase Agreement) and capitalized terms used herein without definitions shall have the meanings specified therefore in such Purchase Agreement; and

WHEREAS, Boeing and Customer desire to add Letter Agreement No. AAL-PA-1977-LA-1502819 entitled [*CTR] to the Purchase
Agreement;

NOW THEREFORE, in consideration of the mutual covenants herein contained, the parties agree to amend the Purchase Agreement as follows:



|1. | Table of Contents:
|-- | ------------------

The Table of Contents to the Purchase Agreement
referencing SA-38 in the footer is deleted in its entirety and is replaced with the new Table of Contents (attached hereto) referencing SA-39 in the footer. Such new Table of Contents is hereby incorporated into the Purchase
Agreement in replacement of its predecessor.



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|------------- |  | ----- |  | ------
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|AAL           |  |       |  |       

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|2. | Letter Agreements:
|-- | ------------------

Letter Agreement No. AAL-PA-1977-LA-1502819 entitled
[*CTR] is hereby incorporated into and made a part of the Purchase Agreement.

[This space intentionally left blank]



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|------------- |  | ----- |  | ------
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EXECUTED IN DUPLICATE as of the day and year first above written.



|                       |  |  |  |                            
|---------------------- |  |  |  | ---------------------------
|THE BOEING COMPANY     |  |  |  | AMERICAN AIRLINES, INC.    
|                       |  | 
|/s/ The Boeing Company |  |  |  | /s/ American Airlines, Inc.
|Signature              |  |  |  | Signature                  
|                       |  | 
|The Boeing Company     |  |  |  | American Airlines, Inc.    
|Printed name           |  |  |  | Printed name               
|                       |  | 
|Attorney-in-Fact       |  |  |  | Vice President & Treasurer 
|Title                  |  |  |  | Title                      



|                  |  |       |  |       
|----------------- |  | ----- |  | ------
|P.A. No. 1977 AAL |  | SA-39 |  | Page 3

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---

TABLE OF CONTENTS



|                      |  |                                                                                           |  |           |       | 
|--------------------- |  | ----------------------------------------------------------------------------------------- |  | --------- | ----- | 
|ARTICLES              |  |                                                                                           |  | SA
NUMBER |      
|                      |  |                                                                                          
|1.                    |  | Quantity, Model and Description                                                           |  |           | SA-21 | 
|2.                    |  | Delivery Schedule                                                                         |  |           |       | 
|3.                    |  | Price                                                                                     |  |           |       | 
|4.                    |  | Payment                                                                                   |  |           |       | 
|5.                    |  | Miscellaneous                                                                             |  |           |       | 
|                      |  |                                                                                          
|TABLE                 |  |                                                                                           |  |           |      
|                      |  |                                                                                          
|1                     |  | Aircraft Delivery, Description, Price and Advance Payments                                |  |           | SA-29 | 
|                      |  |                                                                                          
|1A                    |  | Aircraft Delivery, Description, Price and Advance Payments  [*CTR]                       |  |           | SA-33 | 
|                      |  |                                                                                          
|1B                    |  | Aircraft Delivery, Description, Price and Advance Payments  Exercised MADP Aircraft      |  |           | SA-33 | 
|                      |  |                                                                                          
|1C                    |  | Aircraft Delivery, Description, Price and Advance Payments  [*CTR]                       |  |           | SA-33 | 
|                      |  |                                                                                          
|1D                    |  | Aircraft Delivery, Description, Price and Advance Payments  Boeing Sky Interior
Aircraft |  |           | SA-33 | 
|                      |  |                                                                                          
|1E                    |  | Aircraft Delivery, Description, Price and Advance Payments 
SA-34 Exercised Aircraft     |  |           | SA-34 | 
|                      |  |                                                                                          
|1F                    |  | Aircraft Delivery, Description, Price and Advance Payments  Purchased Aircraft           |  |           | SA-38 | 
|                      |  |                                                                                          
|EXHIBITS              |  |                                                                                           |  |           |      
|                      |  |                                                                                          
|A                     |  | Aircraft Configuration                                                                    |  |           |       | 
|                      |  |                                                                                          
|A1                    |  | Aircraft Configuration                                                                    |  |           | SA-33 | 
|                      |  |                                                                                          
|A2                    |  | Aircraft Configuration                                                                    |  |           | SA-33 | 
|                      |  |                                                                                          
|B                     |  | Aircraft Delivery Requirements and Responsibilities                                       |  |           |       | 
|                      |  |                                                                                          
|C                     |  | Defined Terms                                                                             |  |           |       | 
|                      |  |                                                                                          
|SUPPLEMENTAL EXHIBITS |  |                                                                                           |  |           |      
|                      |  |                                                                                          
|AE1                   |  | Escalation Adjustment Airframe and Optional Features                                      |  |           | SA-20 | 
|                      |  |                                                                                          
|BFE1                  |  | BFE Variables                                                                             |  |           | SA-35 | 
|                      |  |                                                                                          
|CS1                   |  | Customer Support Variables                                                                |  |           |       | 
|                      |  |                                                                                          
|SLP1                  |  | Service Life Policy Components                                                            |  |           |       | 
|                      |  |                                                                                          
|EE1                   |  | Engine Escalation, Engine Warranty and Patent Indemnity                                   |  |           |       | 



|              |  |                   |  |       
|------------- |  | ----------------- |  | ------
|P.A. No. 1977 |  |                   |  | SA-39 
|AAL           |  | Table of Contents |  | Page 1

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TABLE OF CONTENTS, continued



|                       |  |                                                                   |  |          |       | 
|---------------------- |  | ----------------------------------------------------------------- |  | -------- | ----- | 
|LETTER AGREEMENTS      |  |                                                                   |  | SANUMBER |      
|                       |  |                                                                  
|6-1162-AKP-070         |  | Miscellaneous Commitments for Model 737, 757,767 and 777 Aircraft |  |          |       | 
|                       |  |                                                                  
|6-1162-AKP-072R1       |  | [*CTR]                                                            |  |          |       | 
|                       |  | Terminated Per AAL-PA-1977-LA-1105595                             |  |          |       | 
|                       |  |                                                                  
|6-1162-AKP-073         |  | Accident Claims and Litigation                                    |  |          |       | 
|                       |  |                                                                  
|6-1162-AKP-074R2       |  | Business Considerations                                           |  |          |       | 
|                       |  |                                                                  
|6-1162-AKP-075R1       |  | Aircraft Purchase Rights and Substitution Rights                  |  |          | SA-35 | 
|                       |  | - Attachment A                                                    |  |          | SA-35 | 
|                       |  | - Attachment B                                                    |  |          | SA-35 | 
|                       |  | - Attachment C                                                    |  |          | SA-35 | 
|                       |  |                                                                  
|6-1162-AKP-076         |  | Aircraft Performance Guarantees                                   |  |          |       | 
|                       |  |                                                                  
|6-1162-AKP-077         |  | Spares Matters                                                    |  |          |       | 
|                       |  |                                                                  
|6-1162-AKP-078         |  | Model 737 Miscellaneous Commitments                               |  |          |       | 
|                       |  |                                                                  
|6-1162-AKP-079         |  | [*CTR]                                                            |  |          |       | 
|                       |  |                                                                  
|6-1162-AKP-080         |  | Installation of Cabin Systems Equipment                           |  |          |       | 
|                       |  |                                                                  
|6-1162-AKP-081         |  | Model 737 Maintenance Cost Commitment                             |  |          |       | 
|                       |  |                                                                  
|6-1162-AKP-082         |  | Confidentiality                                                   |  |          |       | 
|                       |  |                                                                  
|6-1162-AKP-083         |  | Model 737 Introduction Cost Commitment                            |  |          |       | 
|                       |  |                                                                  
|6-1162-AKP-084         |  | Performance Retention Commitment                                  |  |          |       | 
|                       |  |                                                                  
|6-1162-AKP-085         |  | Component Reliability Commitments                                 |  |          |       | 
|                       |  |                                                                  
|6-1162-AKP-117         |  | Delivery Schedule                                                 |  |          |       | 
|                       |  |                                                                  
|6-1162-SSM-1405R1      |  | Multiple Operating Weight Program Attachment B                    |  |          | SA-35 | 
|                       |  | - Attachment B                                                    |  |          | SA-35 | 
|                       |  |                                                                  
|6-1162-CLO-1035        |  | Aircraft Performance Guarantees                                   |  |          | SA-28 | 
|                       |  |                                                                  
|AAL-PA-1977-LA-1105509 |  | Aircraft Performance Guarantees, 737-700                          |  |          | SA-35 | 
|                       |  |                                                                  
|AAL-PA-1977-LA-1105511 |  | Aircraft Performance Guarantees, 737-900ER                        |  |          | SA-35 | 



|              |  |                   |  |       
|------------- |  | ----------------- |  | ------
|P.A. No. 1977 |  |                   |  | SA-39 
|AAL           |  | Table of Contents |  | Page 2

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---

TABLE OF CONTENTS, continued



|                             |  |                                               |  |          |       | 
|---------------------------- |  | --------------------------------------------- |  | -------- | ----- | 
|LETTER AGREEMENTS, Continued |  |                                               |  | SANUMBER |      
|                             |  |                                              
|6-1162-CLO-1038              |  | Advance Payments and Permitted Transactions   |  |          | SA-31 | 
|                             |  |                                              
|6-1162-CLO-1082              |  | Advance Payments and Permitted Transactions 2 |  |          | SA-32 | 
|                             |  |                                              
|AAL-PA-1977-LA-01073         |  | Advance Payments and Permitted Transactions 3 |  |          | SA-34 | 
|                             |  |                                              
|AAL-PA-1977-LA-1105271       |  | Advance Payments and Permitted Transactions 4 |  |          | SA-35 | 
|                             |  |                                              
|AAL-PA-1977-LA-1105272R1     |  | Business Considerations 2                     |  |          | SA-36 | 
|                             |  |                                              
|AAL-PA-1977-LA-1105616       |  | Open Configuration Matters                    |  |          | SA-35 | 
|                             |  |                                              
|AAL-PA-1977-LA-1105863       |  | Performance Guarantees for Rights Aircraft    |  |          | SA-35 | 
|                             |  |                                              
|AAL-PA-1977-LA-08834         |  | Business Considerations 3                     |  |          | SA-36 | 
|                             |  |                                              
|AAL-PA-1977-LA-08835         |  | [*CTR]                                        |  |          | SA-36 | 
|                             |  |                                              
|AAL-PA-1977-LA-1106665       |  | [*CTR]                                        |  |          | SA-36 | 
|                             |  |                                              
|AAL-PA-1977-LA-1106666       |  | [*CTR]                                        |  |          | SA-36 | 
|                             |  |                                              
|AAL-LA-1106678               |  | Assignment Matters                            |  |          | SA-36 | 
|                             |  |                                              
|AAL-PA-1977-LA-1502819       |  | [*CTR]                                        |  |          | SA-39 | 



|              |  |                   |  |       
|------------- |  | ----------------- |  | ------
|P.A. No. 1977 |  |                   |  | SA-39 
|AAL           |  | Table of Contents |  | Page 3

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LOGO

AAL-PA-1977-LA-1502819

American Airlines, Inc.

PO Box 619616

Fort Worth, Texas 76155-9616



|Attention: | Mr. Cliff Eiland
|---------- | ----------------

Sr. Analyst, Fleet Transactions

Mr. Jay Hancock

Managing
Director, Fleet Transactions



|Subject: | [*CTR]
|-------- | ------



|Reference: | a.) Purchase Agreement No. 1977 (Purchase Agreement) between The Boeing Company (Boeing) and American Airlines, Inc. (Customer) relating to Model 737-823 aircraft
|---------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------

b) AGTA-AAL (AGTA) between Boeing and Customer

This letter agreement (Letter Agreement) is entered into on the date below, and amends and supplements the Purchase Agreement. All
capitalized terms used herein but not otherwise defined in this Letter Agreement have the same meaning as in the Purchase Agreement.

Customer has [*CTR] Boeing to [*CTR] Customer to [*CTR], including all [*CTR] (collectively, [*CTR]) for [*CTR] aircraft. Customer plans to
[*CTR] aircraft and [*CTR]. The parties shall [*CTR] the Aircraft on which such [*CTR].

Boeing has agreed to [*CTR] on the Aircraft
subject to the conditions contained in this Letter Agreement.

1. Customer will [*CTR] (Supplier) to:

1.1. Completely [*CTR] (including all [*CTR] (collectively, [*CTR]), consistent with new [*CTR]. Any [*CTR].

1.2. Do each of the following [*CTR]: (a) [*CTR], (b) [*CTR], (c) [*CTR], and (d) [*CTR] to Boeing.

2. The [*CTR] will be [*CTR] Boeing and Customer representatives per the [*CTR]. Beyond the current [*CTR] will also be [*CTR].

2.1. Any (a) [*CTR] or (b) other [*CTR] discovered during such [*CTR] (to the [*CTR] (i) in order to [*CTR] or (ii) as otherwise [*CTR]), and
such [*CTR] (if applicable) will be [*CTR]. For the avoidance of doubt, Customer may [*CTR] (in Customers sole discretion) [*CTR].

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LOGO

2.2. Customer shall cause [*CTR] one (1) [*CTR] to Boeing. The [*CTR] must include a list of all
[*CTR]. Supplier shall [*CTR].

2.3. Prior to [*CTR], Customer will [*CTR].

3. Upon [*CTR] as follows:

3.1. Customer and Boeing will [*CTR]. If any such [*CTR], Boeing shall [*CTR]; however, other than is set forth in this Section 3.1, in
[*CTR]. At the time of Aircraft delivery, to the extent Customer and Boeing have [*CTR], Customer will [*CTR].

3.2. Similar to
Boeings responsibility for [*CTR], upon Customers [*CTR], Boeing shall be [*CTR].

4. Boeing will [*CTR] on the applicable
Aircraft. Aircraft with [*CTR] will be delivered to Customer with [*CTR].

5. Customer will be responsible for [*CTR] on the Aircraft with
[*CTR] delivery of such Aircraft.

6. Boeing will [*CTR].

7. Customer shall cause [*CTR].

8. Boeing will [*CTR].

9.
Customer will [*CTR] with the terms and conditions of this Letter Agreement.

10. Confidential Treatment.

The information contained herein represents confidential business information and has value precisely because it is not available generally or
to other parties. Customer will limit the disclosure of its contents in accordance with Letter Agreement 6-1162-AKP-082 entitled Confidentiality.

[Remainder of Page Intentionally Left Blank]

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|     |  |                                                        
|---- |  | -------------------------------------------------------
|LOGO |  | The Boeing Company P.O. Box 3707
Seattle, WA 98124-2207



Very truly yours,



|                            |  |                              |  | 
|--------------------------- |  | ---------------------------- |  | 
|THE BOEING COMPANY         
|                            | 
|By                          |  | /s/ The Boeing Company      
|Its                         |  | Attorney-In-Fact            
|                           
|ACCEPTED AND AGREED TO this
|                            | 
|Date:                       |  | June 2, 2016                
|                           
|AMERICAN AIRLINES, INC.    
|                            | 
|By                          |  | /s/ American Airlines, Inc. 
|Its                         |  | Vice President and Treasurer

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BOEING
PROPRIETARY