Code of Federal Regulations Title 41. Public Contracts and Property Management § 41.301–10.135 When must I travel using U.S. flag air carrier service?

(a) Use of a foreign air carrier is determined to be a matter of necessity in accordance with § 301–10.138;  or

(b) The transportation is provided under a bilateral or multilateral air transportation agreement to which the United States Government and the government of a foreign country are parties, and which the Department of Transportation has determined meets the requirements of the Fly America Act.

(c) You are an officer or employee of the Department of State, or the United States Agency for International Development, and your travel is paid with funds appropriated to one of these agencies, and your travel is between two places outside the United States;  or

(d) No U.S. flag air carrier provides service on a particular leg of the route, in which case foreign air carrier service may be used, but only to or from the nearest interchange point on a usually traveled route to connect with U.S. flag air carrier service;  or

(e) A U.S. flag air carrier involuntarily reroutes your travel on a foreign air carrier;  or

(f) Service on a foreign air carrier would be three hours or less, and use of the U.S. flag air carrier would at least double your en route travel time;  or

(g) When the costs of transportation are reimbursed in full by a third party, such as a foreign government, international agency, or other organization.