The British Aerospace Harrier II is a second-generation vertical/short takeoff and landing (V/STOL) jet aircraft used previously by the Royal Air Force (RAF) and, between 2006 and 2010, the Royal Navy (RN). The aircraft was the latest development of the Harrier family, and was derived from the McDonnell Douglas AV-8B Harrier II. Initial deliveries of the Harrier II were designated in service as Harrier GR5; subsequently upgraded airframes were redesignated accordingly as GR7 and GR9. Under the Joint Force Harrier organisation, both the RAF and RN operated the Harrier II under the RAF's Air Command, including deployments on board the navy's s. The Harrier II participated in numerous conflicts, making significant contributions in combat theatres such as Kosovo, Iraq, and Afghanistan. The type's main function was as a platform for air interdiction and close air support missions; the Harrier II was also used for power projection and reconnaissance duties. The Harrier II served alongside the Sea Harrier in Joint Force Harrier. In December 2010, budgetary pressures led to the early retirement of all Harrier IIs from service, at which point it was the last of the Harrier derivatives remaining in British service. In March 2011, the decision to retire the Harrier was controversial as there was no immediate fixed-wing replacement in its role or fixed-wing carrier-capable aircraft left in service at the time; in the long term, the Harrier II was replaced by the Lockheed Martin F-35B Lightning II. Design and development Origins Development of a much more powerful successor to the Harrier began in 1973 as a cooperative effort between McDonnell Douglas (MDD) in the US and Hawker Siddeley (in 1977, its aviation interests were nationalised to form part of British Aerospace) in the UK. First-generation Harriers were being introduced into Royal Air Force and United States Marine Corps; operational experience had highlighted demand for a more capable aircraft. The British government had only a minor requirement, for up to 60 Harriers at most and competing pressures on the defence budget left little room for frivolous expenditure such as the Advanced Harrier. A lack of government backing for developing the necessary engine of the new aircraft, the Pegasus 15, led Hawker to withdraw from this project in 1975. Due to US interest, work proceeded on the development of a less ambitious successor, a Harrier fitted with a larger wing and making use of composite materials in its construction. Two