14 CFR 296.3: Indirect cargo air carrier.

An indirect cargo air carrier is any U.S. citizen who undertakes to engage indirectly in air transportation of property, and uses for the whole or any part of such transportation the services of an air carrier or a foreign air carrier that directly engages in the operation of aircraft under a certificate, regulation, order, or permit issued by the Department of Transportation or its predecessor to the extent that those actions, by law, are still in effect, or the services of its agent, or of another indirect cargo air carrier.