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
British Aerospace Sea Harrier in 1973, and are now popularly recognised as aircraft carriers. Almost immediately upon their construction, a ski-jump was added to the end of the 170-metre deck, enabling the carriers to effectively operate a small number of V/STOL jets. The Royal Air Force's Hawker Siddeley Harrier GR1s had entered service in April 1969. A navalised variant of the Harrier was developed by Hawker Siddeley to serve on the upcoming ships; this became the Sea Harrier. In 1975, the Royal Navy ordered 24 Sea Harrier "FRS.1" (standing for 'Fighter, Reconnaissance, Strike') aircraft, the first of which entered service in 1978. During this