Hawker Siddeley much larger firms. Out of this decision, came the "order" that all future contracts being offered had to include agreements to merge companies. In 1959, Folland Aircraft was acquired, followed by de Havilland Aircraft Company and Blackburn Aircraft in 1960. In 1963, the names of the constituent companies were dropped, with products being rebranded as ""Hawker Siddeley"" or ""HS"". In this period, the company developed the first operational, and, by far, the most successful VTOL jet aircraft, the Harrier family. This aircraft remained in production into the 1990s and remains in service. In 1948, Hawker Siddeley acquired a factory in
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,