Exhibit 10.24 CERTAIN IDENTIFIED INFORMATION HAS BEEN EXCLUDED FROM THE EXHIBIT BECAUSE IT IS BOTH NOT MATERIAL AND IS THE TYPE THAT THE REGISTRANT TREATS AS PRIVATE OR CONFIDENTIAL. OMITTED INFORMATION HAS BEEN REPLACED WITH ASTERISKS. Supplemental Agreement No. 6 to Purchase Agreement No. 3860 between The Boeing Company and United Airlines, Inc. Relating to Boeing Model 787 Aircraft THIS SUPPLEMENTAL AGREEMENT, entered into as of December 31, 2015, by and between THE BOEING COMPANY (Boeing) and UNITED AIRLINES, INC. (a Delaware corporation formerly known as Continental Airlines, Inc. and successor by merger to United Air Lines, Inc.) (Customer); WHEREAS, the parties hereto entered into Purchase Agreement No. 3860 dated September 27, 2012, as amended and supplemented (Purchase Agreement), relating to the purchase and sale of Boeing model 787 aircraft (Aircraft). This Supplemental Agreement is an amendment to the Purchase Agreement; WHEREAS, through *** Supplemental Agreement Number 5 to the Purchase Agreement, *** dated May 12, 2015, Boeing and Customer agreed to *** firm 787-*** aircraft for *** 787-*** aircraft and to *** 787-*** firm aircraft with *** 787-***; WHEREAS, consistent with such prior transactions Boeing and Customer now agree to a *** of *** firm 787-*** aircraft for *** firm 787-*** aircraft and to the *** of these *** 787-*** firm aircraft with *** 787-*** as follows: (i) Boeing and Customer agree to *** Firm 787-*** Aircraft to the Purchase Agreement as Block C Aircraft as such terms are defined in *** and are further identified in Figure 1 below. Figure 1 Delivery Month *** *** UAL-PA-3860 SA-6 Page 1 BOEING / UNITED AIRLINES, INC. PROPRIETARY (ii) Boeing and Customer agree to *** the following *** 787-*** Firm Aircraft and *** them with *** 787-*** Aircraft in the delivery months with option exercise expiry dates as specified below: Model *** Firm Aircraft Delivery Month *** Aircraft Delivery Month** Option Exercise Expiry Date *** *** *** *** *** *** *** *** ** - The nominal delivery month above is subject to revision by plus or minus one month. Boeing will advise Customer of the scheduled delivery month at the time of Customer’s exercise of its rights. WHEREAS, Boeing and Customer agree to apply *** 787-*** previously Firm Aircraft *** under this Supplemental Agreement No. 6 *** for the *** new model 787-*** Aircraft added under this Supplemental Agreement No. 6; and *** Customer’s *** of Supplemental Agreement No. 6 after application of *** (as that term is defined in Letter Agreement No. *** entitled “Option Aircraft” ***) received by Boeing from Customer. 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” is deleted in its entirety and replaced with the attached “Table of Contents” (identified by “SA-6”). 2. Tables. 2.1. “Table 1”, 787-10 Aircraft with GENX-1B*** Engines Delivery, Description, Price and Advance Payments, is deleted in its entirety and replaced with the attached similarly titled “Table 1” (identified by “SA-6”). 2.2. “Table 1, 787-9 Aircraft Delivery, Description, Price and Advance Payments for *** Firm 787-9 Aircraft” (identified by “SA-6”) is added to the Purchase Agreement. 3. Letter Agreements. 3.1. Attachment B-1 to Letter Agreement UAL-PA-03860-LA-1209265R1 entitled “787-10 with GENX-1B*** Engines: Option Aircraft Delivery, Description, Price and Advance Payments” is deleted in its entirety and replaced with the attached Attachment B-1 (identified by “SA-6”). UAL-PA-3860 SA-6 Page 2 BOEING / UNITED AIRLINES, INC. PROPRIETARY 3.2. Letter Agreement UAL-PA-03860-LA-1209413A1R1 entitled “Special Matters — Amendment 1” is deleted in its entirety and replaced with the attached similarly titled Letter Agreement UAL-PA-03860-LA-1209413A1R2 (identified by “SA-6”). The Purchase Agreement will be deemed to be supplemented to the extent herein provided as of the date hereof and as so supplemented will continue in full force and effect. The rest of this page is left intentionally blank. UAL-PA-3860 SA-6 Page 3 BOEING / UNITED AIRLINES, INC. PROPRIETARY EXECUTED IN DUPLICATE as of the day and year first written above. THE BOEING COMPANY UNITED AIRLINES, INC. Signature Signature /s/ I. L. Krueger /s/ Gerald Laderman Printed Name Printed Name Attorney-in-Fact Senior Vice President - Finance and acting Chief Financial Officer Title Title UAL-PA-3860 SA-6 Page 4 BOEING / UNITED AIRLINES, INC. PROPRIETARY

TABLE OF CONTENTS ARTICLES SA NUMBER Article 1. Quantity, Model and Description SA-1 Article 2. Delivery Schedule SA-1 Article 3. Price SA-1 Article 4. Payment SA-1 Article 5. Additional Terms SA-1 TABLE 1. 787-8 with GENX-1B*** Engines Aircraft Information Table *** SA-3 1. 787-9 with GENX-1B*** Engines Aircraft Information Table *** SA-5 1 Table 1, 787-*** Aircraft Delivery, Description, Price and Advance Payments for *** Firm 787-*** Aircraft SA-6 1. 787-10 with GENX-1B*** Engines Aircraft Information Table SA-6 EXHIBITS A1. 787-8 Aircraft Configuration *** A2. 787-9 Aircraft Configuration *** SA-4 A3. 787-10 Aircraft Configuration SA-1 B. Aircraft Delivery Requirements and Responsibilities SUPPLEMENTAL EXHIBITS AE1. Escalation Adjustment/Airframe and Optional Features BFE1. BFE Variables SA-1 CS1. Customer Support Document EE1. Engine Escalation/Engine Warranty *** SLP1. Service Life Policy Components P.A. 3860 TABLE OF CONTENTS, Page 1 of 5 SA-6 BOEING/UNITED AIRLINES, INC. PROPRIETARY TABLE OF CONTENTS, CONTINUED LETTER AGREEMENTS SA NUMBER UAL-PA-03860-LA-1209247 787 e-Enabling UAL-PA-03860-LA-1209264 Open Configuration Matters UAL-PA-03860-LA-1209265R1 Option Aircraft SA-1 Attachment A, 787-*** Option Aircraft Delivery, Description, Price and Advance Payments (DELETED) SA-1 Attachment B-1, 787-*** with GENX-1B*** Engines: Option Aircraft Delivery, Description, Price and Advance Payments SA-6 Attachment B-2, 787-*** with TRENT1000-*** Engines: Option Aircraft Delivery, Description, Price and Advance Payments (DELETED) SA-3 UAL-PA-03860-LA-1209409 Spare Parts Initial Provisioning UAL-PA-03860-LA-1209410 Special Matters Relating to COTS Software and End User License Agreements UAL-PA-03860-LA-1209411 Special Terms – Seats and In-flight Entertainment UAL-PA-03860-LA-1209417 Model 787 Post-Delivery Software & Data Loading CONFIDENTIAL LETTER AGREEMENTS UAL-PA-03860-LA-1209236R1 Model Substitution SA-1 Attachment A, 787-9 Airframe Pricing of Substitution Aircraft with General Electric GEnx-1B*** and Rolls Royce Trent 1000-*** engines SA-1 Attachment B, 787-10 with General Electric GEnx-1B*** and Rolls Royce TRENT 1000-*** Engines SA-1 Attachment C, 787-8 with General Electric GEnx-1B*** and Rolls Royce TRENT 1000-*** SA-1 P.A. 3860 TABLE OF CONTENTS, Page 2 of 4 SA-6 BOEING / UNITED AIRLINES, INC. PROPRIETARY TABLE OF CONTENTS, CONTINUED CONFIDENTIAL LETTER AGREEMENTS, continued SA NUMBER UAL-PA-03860-LA-1209412 Spare Parts Commitment UAL-PA-03860-LA-1209413R1 Special Matters SA-1 UAL-PA-03860-LA-1209413A1R2 Special Matters – Amendment 1 SA-6 UAL-PA-03860-LA-1209414 Other Special Matters UAL-PA-03860-LA-1209413A1 Other Special Matters - Amendment 1 SA-1 UAL-PA-03860-LA-1209416R1 Promotional Support SA-2 UAL-PA-03860-LA-1209430 Performance Guarantees UAL-PA-03860-LA-1209455 *** – TERMINATED SA-1 UAL-PA-03860-LA-1209429 *** UAL-PA-03860-LA-1209618R1 Alternate Engine Selection SA-1 6-1162-ELP-0794 *** Program- *** Aircraft 6-1162-ELP-0795 *** Program- *** Aircraft UAL-PA-03860-LA-1301368 Performance Guarantees (787-10) SA-1 UAL-PA-03860-LA-1301373 787-10 Aircraft Open Configuration and Other Matters SA-1 UAL-PA-03860-LA-1301375 Provisions Relating to Customer’s *** for 787-10 Aircraft SA-1 UAL-PA-03860-LA-1301377 787-10 *** SA-1 UAL-PA-03860-LA-1301377A1 787-10 *** – Amendment 1 SA-4 UAL-PA-03860-LA-1301380 787-10 Program Launch SA-1 UAL-PA-03860-LA-1500017 Demonstration Flight Waiver SA-4 UAL-PA-03860-LA-1500059 Installation of Cabin Systems Equipment SA-4 P.A. 3860 TABLE OF CONTENTS, Page 3 of 4 SA-6 BOEING / UNITED AIRLINES, INC. PROPRIETARY SUPPLEMENTAL AGREEMENTS DATED AS OF Supplemental Agreement No. 1 June 17, 2013 Supplemental Agreement No. 2 December 16, 2013 Supplemental Agreement No. 3 July 22, 2014 Supplemental Agreement No. 4 January 14, 2015 Supplemental Agreement No. 5 May 12, 2015 Supplemental Agreement No. 6 December 31, 2015 P.A. 3860 TABLE OF CONTENTS, Page 4 of 4 SA-6 BOEING / UNITED AIRLINES, INC. PROPRIETARY

Table 1 to Purchase Agreement No. 3860 787-10 Aircraft with GENX-1B*** Engines Delivery, Description, Price and Advance Payments (787-10/GE/***) Airframe Model/MTOW: 787-10 *** pounds Detail Specification: *** Engine Model/Thrust: GENX-1B***1 *** pounds Airframe Price Base Year/Escalation Formula: *** *** Airframe Price: $ *** Engine Price Base Year/Escalation Formula: *** *** Optional Features: $ *** Airframe Escalation Data: Sub-Total of Airframe and Features: $ *** Base Year Index (ECI): *** Engine Price (Per Aircraft) : $ ***1 Base Year Index (CPI): *** Aircraft Basic Price (Excluding BFE/SPE): $ *** Engine Escalation Data: Buyer Furnished Equipment (BFE) Estimate: $ *** Base Year Index (ECI): *** In-Flight Entertainment (IFE) Estimate: $ *** Base Year Index (CPI): *** Refundable Deposit/Aircraft at Proposal Accept: $ *** Escalation Escalation Serial Number Escalation Estimate Advance Payment Per Aircraft (Amts. Due/Mos. Prior to Delivery): Delivery Number of Factor Factor (Subject to Adv Payment Base *** *** *** *** Date Aircraft (Airframe) (Engine) Change) Price Per A/P *** *** *** *** *** *** *** *** * *** $ *** $ *** $ *** $ *** $ *** *** *** *** *** * *** $ *** $ *** $ *** $ *** $ *** *** *** *** *** * *** $ *** $ *** $ *** $ *** $ *** *** *** *** *** * *** $ *** $ *** $ *** $ *** $ *** *** *** *** *** * *** $ *** $ *** $ *** $ *** $ *** *** *** *** *** * *** $ *** $ *** $ *** $ *** $ *** *** *** *** *** * *** $ *** $ *** $ *** $ *** $ *** *** *** *** *** * *** $ *** $ *** $ *** $ *** $ *** *** *** *** *** * *** $ *** $ *** $ *** $ *** $ *** *** *** *** *** * *** $ *** $ *** $ *** $ *** $ *** *** *** *** *** * *** $ *** $ *** $ *** $ *** $ *** Boeing Proprietary 787-10 with GE Engines Table 1 (SA-6), Page 1 Table 1 to Purchase Agreement No. 3860 787-10 Aircraft with GENX-1B*** Engines Delivery, Description, Price and Advance Payments (787-10/GE/***) Escalation Escalation Serial Number Escalation Estimate Advance Payment Per Aircraft (Amts. Due/Mos. Prior to Delivery): Delivery Number of Factor Factor (Subject to Adv Payment Base *** *** *** *** Date Aircraft (Airframe) (Engine) Change) Price Per A/P *** *** *** *** *** *** *** *** * *** $ *** $ *** $ *** $ *** $ *** *** *** *** *** * *** $ *** $ *** $ *** $ *** $ *** *** *** *** *** * *** $ *** $ *** $ *** $ *** $ *** *** *** *** *** ** *** $ *** $ *** $ *** $ *** $ *** *** *** *** *** ** *** $ *** $ *** $ *** $ *** $ *** *** *** *** *** ** *** $ *** $ *** $ *** $ *** $ *** *** *** *** *** ** *** $ *** $ *** $ *** $ *** $ *** *** *** *** *** ** *** $ *** $ *** $ *** $ *** $ *** *** *** *** *** ** *** $ *** $ *** $ *** $ *** $ *** *** *** *** *** ** *** $ *** $ *** $ *** $ *** $ *** Total: 23 1 Engine model, thrust and pricing are subject to *** to deliver GEnx-1B*** thrust rating at GEnx-1B*** price. * *** Escalation Factors*** ** *** Escalation Factors*** Boeing Proprietary 787-10 with GE Engines Table 1 (SA-6), Page 2 Table 1 to Purchase Agreement No. 3860 787-9 Aircraft Delivery, Description, Price and Advance Payments for *** Firm 787-9 Aircraft (787-9/GE/***) Airframe Model/MTOW: 787-9 *** pounds1 Detail Specification: *** Engine Model/Thrust: GENX-1B***2 *** pounds Airframe Price Base Year/Escalation Formula: *** *** Airframe Price: $ *** Engine Price Base Year/Escalation Formula: *** *** Optional Features: $ *** Airframe Escalation Data: Sub-Total of Airframe and Features: $ *** Base Year Index (ECI): *** Engine Price (Per Aircraft): $ *** Base Year Index (CPI): *** Aircraft Basic Price (Excluding BFE/SPE): $ *** Engine Escalation Data: Buyer Furnished Equipment (BFE) Estimate: $ *** Base Year Index (ECI): *** In-Flight Entertainment (IFE) Estimate: $ *** Base Year Index (CPI): *** Scheduled Number Escalation Escalation Escalation Estimate Advance Payment Per Aircraft (Amts. Due/Mos. Prior to Delivery): Delivery of Factor Factor Serial Adv Payment Base *** *** *** *** Date Aircraft (Airframe) (Engine) Number Price Per A/P *** *** *** *** Block C Aircraft 1,2,3 *** *** *** *** *** $ *** $ *** $ *** $ *** $ *** *** *** *** *** *** $ *** $ *** $ *** $ *** $ *** Total Block C *** 1 MTOW provided in accordance with MTOW Article 3.2 of Letter Agreement 6-1162-RCN-1936. 2 Conditional on a GE agreement to deliver Genx-1B*** thrust rating at the Genx-1B*** price. 3 The Block C Aircraft shall be considered Block B Aircraft as defined pursuant to *** for purposes of Letter Agreement 6-1162-RCN entitled “***”. 4 The *** 787-9 Aircraft specified above are “Block C Aircraft” as such term is defined in ***, as amended and supplemented ***. APR 71359 Boeing / United Airlines, Inc. Proprietary 787-9 Table 1, Page 1, SA-6 Attachment B-1 to Letter Agreement UAL-PA-03860-LA-120965R1 787-10 Option Aircraft with GENX-1B*** Engines Delivery, Description, Price and Advance Payments (787-10/GE/***) Airframe Model/MTOW: 787-10 *** pounds Detail Specification: *** Engine Model/Thrust: GENX-1B***¹ *** pounds Airframe Price Base Year/Escalation Formula: *** *** Airframe Price: $ *** Engine Price Base Year/Escalation Formula:2 *** *** Optional Features: $ *** Airframe Escalation Data: Sub-Total of Airframe and Features: $ *** Base Year Index (ECI): *** Engine Price (Per Aircraft): $ ***1 Base Year Index (CPI): *** Aircraft Basic Price (Excluding BFE/SPE): $ *** Engine Escalation Data: Buyer Furnished Equipment (BFE) Estimate: $ *** Base Year Index (ECI): *** In-Flight Entertainment (IFE) Estimate: $ *** Base Year Index (CPI): *** Non-Refundable Deposit/Aircraft at Def Agreement $ *** Escalation Escalation Option Exercise Escalation Estimate Advance Payment Per Aircraft (Amts. Due/Mos. Prior to Delivery): Delivery Number of Factor Factor Expiry Adv Payment Base *** *** *** *** Date Aircraft (Airframe) (Engine) Date Price Per A/P *** *** *** *** ***++ *** *** *** *** $ *** $ *** $ *** $ *** $ *** ***++ *** *** *** *** $ *** $ *** $ *** $ *** $ *** *** *** *** *** *** $ *** $ *** $ *** $ *** $ *** *** *** *** *** *** $ *** $ *** $ *** $ *** $ *** *** *** *** *** *** $ *** $ *** $ *** $ *** $ *** *** *** *** *** *** $ *** $ *** $ *** $ *** $ *** *** *** *** *** *** $ *** $ *** $ *** $ *** $ *** *** *** *** *** *** $ *** $ *** $ *** $ *** $ *** APR64695-1F.TXT Boeing Proprietary 787-10 with GE Engines Table 1 (SA-6), Page 1

Attachment B-1 to Letter Agreement UAL-PA-03860-LA-120965R1 787-10 Option Aircraft with GENX-1B*** Engines Delivery, Description, Price and Advance Payments (787-10/GE/***) Escalation Escalation Option Exercise Escalation Estimate Advance Payment Per Aircraft (Amts. Due/Mos. Prior to Delivery): Delivery Number of Factor Factor Expiry Adv Payment Base *** *** *** *** Date Aircraft (Airframe) (Engine) Date Price Per A/P *** *** *** *** *** *** *** *** *** $ *** $ *** $ *** $ *** $ *** *** *** *** *** *** $ *** $ *** $ *** $ *** $ *** *** *** *** *** *** $ *** $ *** $ *** $ *** $ *** *** *** *** *** *** $ *** $ *** $ *** $ *** $ *** *** *** *** *** *** $ *** $ *** $ *** $ *** $ *** *** *** *** *** *** $ *** $ *** $ *** $ *** $ *** *** *** *** *** *** $ *** $ *** $ *** $ *** $ *** *** *** *** *** *** $ *** $ *** $ *** $ *** $ *** *** *** *** *** *** $ *** $ *** $ *** $ *** $ *** *** *** *** *** *** $ *** $ *** $ *** $ *** $ *** *** *** *** *** *** $ *** $ *** $ *** $ *** $ *** Total: *** 1 Engine model, thrust and pricing are subject to *** to deliver GEnx-1B*** thrust rating at GEnx-1B*** price. 2 Base year pricing is subject to engine manufacturer confirmation. * The option exercise expiry date for the *** 787-10 Option Aircraft (as specified above) supersedes §4.1 of Letter Agreement UAL-PA-03860-LA- 1209265R1 entitled “Option Aircraft” ++ The delivery schedule for the *** 787-10 Option Aircraft is a nominal delivery month and is subject to revision by plus or minus one month. Boeing will advise Customer of the scheduled delivery month at the time of Customer’s exercise of its rights. APR 64695-1F.TXT Boeing Proprietary 787-10 with GE Engines Table 1 (SA-6), Page 2 The Boeing Company P.O. Box 3707 Seattle, WA 98124-2207 UAL-PA-03860-LA-1209413A1R2 United Airlines, Inc. 233 South Wacker Drive Chicago, Illinois 60606 Subject: Special Matters — Amendment 1 Reference: Purchase Agreement No. 3860 (Purchase Agreement) between The Boeing Company (Boeing) and United Airlines, Inc. relating to Model 787 aircraft (Aircraft) This letter agreement UAL-PA-03860-LA-1209413A1R2 (Amending Letter Agreement) amends and supplements the Purchase Agreement and amends and supplements certain terms in Letter Agreement UAL-PA-03860-LA-1209413 (the Letter Agreement) ), and supersedes and replaces in its entirety letter agreement UAL -PA -03860 -LA-1209413A1R1. All terms used and not defined in this Letter Agreement have the same meaning as in the Purchase Agreement. 1. Amendments to Article 1 of the Letter Agreement. New Article 1.4 is hereby added as follows: 1.4. The parties agree that the *** 787-*** Aircraft added by SA-6 with delivery months during (i) ***; and (ii) *** shall, if Customer exercises its rights in such 787-*** Aircraft, be deemed to be 787-*** Aircraft for all purposes under the Purchase Agreement and thereby remain entitled to the corresponding 787-*** Aircraft credit memoranda. UAL-PA-03860-LA-1209413A1R2 Page 1 Special Matters SA-6 BOEING / UNITED AIRLINES, INC. PROPRIETARY 2. Amendments to Article 4 of the Letter Agreement. 4.4 Special *** Provisions for the Launch Aircraft. With respect to (i) the *** 787-10 Aircraft listed in Table 1 to the Purchase Agreement as of the effective date of Supplemental Agreement No. 6 to the Purchase Agreement and (ii) the *** 787-*** Aircraft specified in Figure 1 below; (787-10 Aircraft and 787-*** Aircraft specified in (i) and (ii) herein are each a Launch Aircraft), the parties agree that *** of the Article 4.1 *** obligation will be *** delivery of each Launch Aircraft (Launch Aircraft *** Obligation). At time of delivery of each Launch Aircraft, Boeing will *** to *** the Launch Aircraft *** Obligation. Figure 1 Model *** Aircraft Delivery Month/Quarter at the Effective Date of this Letter Agreement 787-*** *** 787-*** *** 787-*** *** 787-*** *** 3. Confidential Treatment. Boeing and Customer understand that certain information contained in this Letter Agreement, including any attachments hereto, is considered by both parties to be confidential. Boeing and Customer agree that each party will treat this Letter Agreement and the information contained herein as confidential and will not, without the other party’s prior written consent, disclose this Letter Agreement or any information contained herein to any other person or entity except as may be required by applicable law or governmental regulations. UAL-PA-03860-LA-1209413A1R2 Page 2 Special Matters SA-6 BOEING / UNITED AIRLINES, INC. PROPRIETARY Very truly yours, THE BOEING COMPANY By: /s/ I. L. Krueger Its: Attorney-In-Fact ACCEPTED AND AGREED TO this Date: December 31, 2015 UNITED AIRLINES, INC. By: /s/ Gerald Laderman Its: Senior Vice President - Finance and acting Chief Financial Officer UAL-PA-03860-LA-1209413A1R2 Page 3 Special Matters SA-6 BOEING / UNITED AIRLINES, INC. PROPRIETARY