Flag operation
(1) Airplanes:
(i) Turbojet-powered airplanes;
(ii) Airplanes having a passenger-seat configuration of more than 9 passenger seats, excluding each crewmember seat; or
(iii) Airplanes having a payload capacity of more than 7,500 pounds.
(2) Locations:
(i) Between any point within the State of Alaska or the State of Hawaii or any territory or possession of the United States and any point outside the State of Alaska or the State of Hawaii or any territory or possession of the United States, respectively;
(ii) Between any point within the 48 contiguous States of the United States or the District of Columbia and any point outside the 48 contiguous States of the United States and the District of Columbia;
(iii) Between any point outside the U.S. and another point outside the U.S.
Source: 14 CFR Federal Aviation Regulations §110.2