14 C.F.R. § 295.20

Air charter brokers are not authorized under this part to hold out, sell, or otherwise arrange charter air transportation to be operated by a person or entity that does not hold the requisite form of economic authority from the Department and appropriate safety authority from the Federal Aviation Administration and, if applicable, a foreign safety authority. Air charter brokers are not authorized under this part to hold out, sell, or arrange air transportation to be performed by a direct air carrier or direct foreign air carrier that the direct carrier is not authorized in its own right to hold out, sell, or operate. Only direct air carriers that are citizens of the United States as defined in 49 U.S.C. 40102(a)(15) may provide direct air transportation operations in interstate or intrastate air transportation.