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 and were inducted the same year. Ten more Sea Harriers were purchased in November 1985; eventually a total of 30 Harriers were procured, 25 for operational use and the remainder as dual-seat trainer aircraft. Until the 1990s, significant portions of pilot training was carried out in Britain due to limited aircraft availability. The introduction of the Sea Harrier allowed for the retirement of India's previous carrier fighter aircraft, the Hawker Sea Hawk, as well as for the Navy's aircraft carrier, INS "Vikrant" (ex-HMS "Hercules"), to be extensively modernised between 1987 and 1989. India has operated Sea Harriers from both the