To what extent should a U.S. Flag Carrier be used?
U.S. Flag Carrier service available at point of origin shall be used to destination or, in the absence of direct or through service, to the farthest interchange point on a usually traveled route. When an origin or interchange point is not served by a U.S. Flag Carrier, foreign-flag air carrier service shall be used only to the nearest interchange point on a usually traveled route to connect with U.S. Flag Carrier service.