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 AV-8A on the pre-existing production lines in the United Kingdom—hence all AV-8A Harriers were purchased from Hawker Siddeley. Improved Harrier versions with better sensors and more powerful engines were developed in later years. The USMC received 102 AV-8A and 8 TAV-8A Harriers between 1971 and 1976. The Harrier was typically used as a ground attack aircraft, though its manoeuvrability also allows it to effectively engage other aircraft at short ranges. The Harrier is powered by a single Pegasus turbofan engine mounted in the fuselage. The engine is fitted with two air intakes and four vectoring nozzles for directing the thrust