41 CFR § 301-53.1 - Using promotional benefits from travel service providers.

Promotional benefits or materials, such as frequent flyer miles may be retained for subsequent official travel or for personal use if such items are obtained under the same conditions as those offered to the general public and at no additional cost to the Government. If an employee is offered such benefits in connection with planning an official conference or other group travel, they are considered property of the Government and cannot be retained for personal use, but may be accepted on behalf of the Government for use on official travel.