Exhibit 10.15 1485-09 July 12, 1996 United Air Lines, Inc. P.O. Box 66100 Chicago, Illinois 60666 Subject: Letter Agreement No. 1485-09 to Purchase Agreement No. 1485 [*CONFIDENTIAL MATERIAL OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION PURSUANT TO A REQUEST FOR CONFIDENTIAL TREATMENT] Reference is made to Purchase Agreement No. 1485 dated October 25, 1988, between The Boeing Company (Boeing) and United Air Lines, Inc. (Buyer) relating to the sale by Boeing and the purchase by Buyer of ninety eight (98) Model 757-222 aircraft (the Purchase Agreement). All terms used herein and in the Purchase Agreement, and not defined herein, shall have the same meaning as in the Purchase Agreement. [*CONFIDENTIAL MATERIAL OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION PURSUANT TO A REQUEST FOR CONFIDENTIAL TREATMENT] United Air Lines, Inc. 1485-09 Page 2 [*CONFIDENTIAL MATERIAL OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION PURSUANT TO A REQUEST FOR CONFIDENTIAL TREATMENT] P.A. No. 1485 United Air Lines, Inc. 1485-09 Page 3 [*CONFIDENTIAL MATERIAL OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION PURSUANT TO A REQUEST FOR CONFIDENTIAL TREATMENT] P.A. No. 1485 United Air Lines, Inc. 1485-09 Page 4 [*CONFIDENTIAL MATERIAL OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION PURSUANT TO A REQUEST FOR CONFIDENTIAL TREATMENT] Very truly yours, THE BOEING COMPANY By /s/ M. O. Hunt -------------- Its Attorney in Fact ---------------- ACCEPTED AND AGREED TO this Date: July 12, 1996 United Air Lines Inc. By /s/ Douglas A. Hacker --------------------- Its Senior Vice President and ------------------------- Chief Financial Officer ----------------------- P.A. No. 1485