14 C.F.R. § 380.2
For the purposes of this part:
Certificated air carrier means a U.S. direct air carrier holding a certificate issued under the statute.
Charter flight means a flight operated under the terms of a charter contract between a direct air carrier and its customer. It does not include scheduled air transportation, scheduled foreign air transportation, or nonscheduled cargo air transportation, sold on an individually ticketed or individually waybilled basis.
Direct air carrier means a certificated commuter or foreign air carrier, or an air taxi operator registered under part 298 of this chapter, or a Canadian charter air taxi operator registered under part 294 of this chapter, that directly engages in the operation of aircraft under a certificate, authorization, permit or exemption issued by the Department.
Educational institution means a school that is operated as such on a year-round basis and is empowered to grant academic degrees or secondary school diplomas by any government in the United States or by a foreign government.
Foreign air carrier means a direct air carrier that holds a foreign air carrier permit issued under the statute or an exemption issued under the statute authorizing direct foreign air transportation.
Foreign Public Charter operator means an indirect air carrier which is not a citizen of the United States as defined in the statute, that is authorized to engage in the formation of groups for transportation on Public Charters in accordance with this part.
Indirect air carrier means any person who undertakes to engage indirectly in air transportation operations and who uses for such transportation the services of a direct air carrier.
Public Charter means a one-way or round-trip charter flight to be performed by one or more direct air carriers that is arranged and sponsored by a charter operator.
Public Charter operator means a U.S. or foreign Public Charter operator.
Security agreement means:
Sub-operator means a Public Charter operator that has contracted for its charter seats from a Public Charter operator that has contracted from one or more direct air carriers. A sub-operator is itself an indirect air carrier, not an agent of the Public Charter operator from which it has obtained its seat.
U.S. Public Charter operator means an indirect air carrier that is a citizen of the United States as defined in 49 U.S.C. 40102(a) and that is authorized to engage in the formation of groups for transportation on Public Charters in accordance with this part.
14 C.F.R. §380.2