48 C.F.R. § 47.401
As used in this subpart-
Air freight forwarder means an indirect air carrier that is responsible for the transportation of property from the point of receipt to the point of destination, and utilizes for the whole or any part of such transportation the services of a direct air carrier or its agent, or of another air freight forwarder.
Gateway airport abroad means the airport from which the traveler last embarks en route to the United States or at which the traveler first debarks incident to travel from the United States.
Gateway airport in the United States means the last U.S. airport from which the traveler's flight departs or the first U.S. airport at which the traveler's flight arrives.
International air transportation means transportation by air between a place in the United States and a place outside the United States or between two places both of which are outside the United States.
United States means the 50 States, the District of Columbia, and outlying areas of the United States.
U.S.-flag air carrier means an air carrier holding a certificate under section 401 of the Federal Aviation Act of 1958 (49 U.S.C. 41102 ).
48 C.F.R. §47.401