Exhibit 4.9

GUARANTEE

dated as of October 13, 2009

from

UAL CORPORATION

Ten (10) Airbus A319-131 Aircraft

Six (6) Airbus A320-232 Aircraft

Seven (7) Boeing 767-322ER Aircraft

Three (3) Boeing 777-222ER Aircraft and

Five (5) Boeing 747-422 Aircraft

TABLE OF CONTENTS

i

GUARANTEE

THIS GUARANTEE , dated as of October 13, 2009 (as amended, modified or supplemented from time to time, this “ Guarantee ”), from UAL CORPORATION , a Delaware corporation (together with its permitted successors and assigns, the “ Guarantor ”), to the parties listed in Schedule I hereto (collectively, together with their successors and permitted assigns, the “ Parties ”, and, individually, a “ Party ”).

WHEREAS , United Air Lines, Inc., a Delaware corporation (“ Owner ”), a direct wholly-owned subsidiary of the Guarantor, has entered into that certain Note Purchase Agreement dated as of October 13, 2009 (the “ Note Purchase Agreement ”) among Owner, Wilmington Trust Company, as pass through trustee under the Pass Through Trust Agreement (the “ Pass Through Trustee ”), Wilmington Trust Company, as Escrow Agent, Wilmington Trust Company, as Paying Agent and Wilmington Trust Company, as Subordination Agent (the “ Subordination Agent ”);

WHEREAS , capitalized used but not defined herein shall have the meanings set forth in the Note Purchase Agreement;

WHEREAS , in order to finance the aircraft identified on Schedule II hereto (the “ Aircraft ”), Owner will issue the Equipment Notes under the Indentures; and

WHEREAS , it is a condition to the purchase of the Equipment Notes by the Pass Through Trustee that the Guarantor execute and deliver this Guarantee.

NOW, THEREFORE , in order to induce the Pass Through Trustee to purchase the Equipment Notes and for other good and valuable consideration, receipt of which is hereby acknowledged, the parties hereto agree as follows:

Section 1.        Guarantee .

(a)      The Guarantor does hereby acknowledge that it is fully aware of the terms and conditions of the Indentures, the Participation Agreements, the Equipment Notes and the transactions and the other documents contemplated thereby, and does hereby irrevocably and fully and unconditionally guarantee, as primary obligor and not as surety merely, to the Parties, as their respective interests may appear, the payment by Owner of all payment obligations when due under the Indentures, the Participation Agreements and the Equipment Notes (such obligations of Owner guaranteed hereby being hereafter referred to, individually, as a “ Guaranteed Obli