The Harrier today is one of the truly and most widely known of V/STOL military aircrafts. When the Harrier II was first flown in the fall of 1981, 21 years had elapsed since the original Hawker P.1127 first flight. The 1957 design for the P.1127 was based on a French engine concept, adopted and improved upon by the British. The project was funded by the British Bristol Engine Co. and by the U.S. Government through the Mutual Weapons Development Program.

With the basic configuration of the engine largely determined and with development work under way, Hawker Aircraft Ltd. engineers directed their attention to designing a V/STOL aircraft that would use the engine. Without government/military customer support, they produced a single-engine attack-reconnaissance plane. Other than the engine's swivelling nozzles, the reaction control system was the only complication in the effort to provide V/STOL capability. The initial P.1127 was rolled out in the summer of 1960, by which time RAF interest in the aircraft had finally resulted in funding by the British Government for the two prototypes. First hovers were made in the fall. With potential NATO and other foreign interest in the P.1127, four additional airplanes were ordered to continue development.

As the project proceeded into the early sixties international interest in V/STOL tactical aircraft led to an agreement to conduct a tripartite operation, with the United Kingdom, West Germany and the United States sharing equally in development and evaluation. Nine P.1127s were ordered and designated Kestrel F.G.A. 1s in the RAF name system. A number of major configuration changes were incorporated in it although the basic concept remained unchanged. Within the United States it was a tri-service venture (Army, Navy, Air Force) .

Before it entered RAF service, the U.S. Marine Corps evinced a major interest in the Harrier for attack missions, and procurement of Marine AV-8As was initiated. The Harrier entered service with the RAF and the U.S. Marines in the early seventies. It was followed in both services by a limited number of two-place trainer versions, designated TAV-8As for the Marines.

Upgrading of the AV-8A with some of the systems improvements of the AV-8B resulted in the AV-8C configuration. Two test aircraft were reconfigured for evaluation and a limited AV-8C conversion program was undertaken.

An ongoing upgrading program for selected Harriers in the inventory will provide new engines and radar, a Forward Looking Infrared Radar (FLIR), moving map and night vision goggles.