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 Hoopoe fitted during the short trial period, two variants of the Bristol Mercury were later replaced by an Armstrong Siddeley Jaguar and Panther with an increase in performance. Trials at Felixstowe in 1929 with floats fitted showed that the aircraft was severely underpowered with the Mercury powerplant, requiring the change to the Jaguar engine. Service interest in the type had waned by autumn 1930 although the single prototype continued in development flying with Armstrong Siddeley and the Royal Aircraft Establishment until 1932 when the Hoopoe was scrapped. Hawker Hoopoe The Hawker Hoopoe was a British prototype naval fighter aircraft designed and