United States Department of Defense aerospace vehicle designation
Joint Regulation 4120.15E: Designating and Naming Military Aerospace Vehicles is the current system for designating all aircraft, helicopters, rockets, missiles, spacecraft, and other aerial vehicles in military use by the United States Armed Forces. == History == United States Department of Defense Directive 4120.15 "Designating and Naming Military Aircraft, Rockets, and Guided Missiles" was originally issued November 24, 1971 and named the Air Force as the Executive Agent empowered to carry out the directive.
Source: Wikipedia — United States Department of Defense aerospace vehicle designation (CC BY-SA 4.0)