Hawker Siddeley Harrier AV-8As to the AV-8C configuration—the work focused mainly on extending useful service lives and improving VTOL performance. The AV-8C and the remaining AV-8A Harriers were retired by 1987. These were replaced by the Harrier II, designated as the AV-8B, which was introduced into service in 1985. The performance of the Harrier in USMC service led to calls for the United States Air Force to procure Harrier IIs in addition to the USMC's own plans, but these never resulted in Air Force orders. Since the late 1990s, the AV-8B has been slated to be replaced by the F-35B variant of the
Hawker Siddeley Harrier Force. Design work on the P.1127 was formally started in 1957 by Sir Sydney Camm, Ralph Hooper of Hawker Aircraft, and Stanley Hooker (later Sir Stanley Hooker) of the Bristol Engine Company. The close cooperation between Hawker, the airframe company, and Bristol, the engine company, was viewed by project engineer Gordon Lewis as one of the key factors that allowed the development of the Harrier to continue in spite of technical obstacles and political setbacks. Rather than using rotors or a direct jet thrust, the P.1127 had an innovative vectored thrust turbofan engine, the Pegasus. The Pegasus I was rated