26 U.S.C. § 4272: Definition of taxable transportation, etc.

For purposes of this part, except as provided in subsection (b), the term “taxable transportation” means transportation by air which begins and ends in the United States. that portion of any transportation which meets the requirements of paragraphs (1), (2), (3), and (4) of section 4262(b), or under regulations prescribed by the Secretary, transportation of property in the course of exportation (including shipment to a possession of the United States) by continuous movement, and in due course so exported. For purposes of this part, the term “property” does not include excess baggage accompanying a passenger traveling on an aircraft operated on an established line. For purposes of this part, the term “transportation” includes layover or waiting time and movement of the aircraft in deadhead service.