Following the Hawker (later British Aerospace) Kestrel operational trials (#19), the first of six production-designed Harrier developmental aircraft flew on 31 August 1966. The production GR1 Harrier entered service with the UK Royal Air Force on 1 April 1969 powered by the 19,000 lb Bristol (later Rolls-Royce) Pegasus Mk 101. US Marine Corps AV-8As were purchased in 1969, powered by the 21,500 lb thrust Pegasus 11.
A navalized version, the FRS1 Sea Harrier, entered service with the Royal Navy in 1980. McDonnell Douglas (later with British Aerospace) began developing the AV-8B GR5 Harrier II in 1974, and began flight testing in 1981.
With a more powerful engine, a larger, composite supercritical wing, optimized Lift Improvement Devices (LIDs) and other improvements, the Harrier II was able to double the payload and range when making short takeoffs. The F402-RR-408 Pegasus 11-61 reached 23,800 lb thrust. In addition to the USMC, the UK RAF and RN, the Harrier has also been operated by Spain, Italy, India and Thailand.
October 21, 1960
P.1127 : First VTOL flight of the Hawker P.1127
November 19, 1960
P.1127 : First untethered hover flight of the Hawker P.1127
November 20, 1970
AV-8A Harrier: First flight of the Hawker AV-8A Harrier
August 20, 1978
FRS.1 Sea Harrier: First flight of the Hawker-Siddeley Sea Harrier FRS.1
August 29, 1987
AV-8B Harrier II: First flight of the production McDonnell Douglas AV-8B Harrier II