Hawker Siddeley Harrier cancelled after the release of the British Government's 1957 Defence White Paper, which advocated a policy shift away from manned aircraft and towards missiles. This policy resulted in the termination of the majority of aircraft development projects then underway for the British military. Hawker sought to quickly move on to a new project and became interested in Vertical Take Off/Landing (VTOL) aircraft, which did not need runways. According to Air Chief Marshal Sir Patrick Hine this interest may have been stimulated by the presence of Air Staff Requirement 345, which sought a V/STOL ground attack fighter for the Royal Air
Hawker Siddeley Harrier that the aircraft were highly effective in combat. These operations also demonstrated that "Harrier Carriers" provided a powerful presence at sea without the expense of big deck carriers. Following the display of Harrier operations from small carriers, the navies of Spain and later Thailand bought the Harrier for use as their main carrier-based fixed-wing aircraft. Spain's purchase of Harriers was complicated by long-standing political friction between the British and Spanish governments of the era; even though the Harriers were manufactured in the UK they were sold to Spain with the US acting as an intermediary. During tests in November 1972,