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
British Aerospace Sea Harrier in 1973, and are now popularly recognised as aircraft carriers. Almost immediately upon their construction, a ski-jump was added to the end of the 170-metre deck, enabling the carriers to effectively operate a small number of V/STOL jets. The Royal Air Force's Hawker Siddeley Harrier GR1s had entered service in April 1969. A navalised variant of the Harrier was developed by Hawker Siddeley to serve on the upcoming ships; this became the Sea Harrier. In 1975, the Royal Navy ordered 24 Sea Harrier "FRS.1" (standing for 'Fighter, Reconnaissance, Strike') aircraft, the first of which entered service in 1978. During this