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
McDonnell Douglas AV-8B Harrier II a demonstration of the Hawker Siddeley Harrier on the Italian Navy ("Marina Militare") helicopter carrier , the country began investigating the possibility of acquiring the Harrier. Early efforts were hindered by a 1937 Italian law that prohibited the navy from operating fixed-wing aircraft because they were the domain of the air force. In early 1989, the law was changed to allow the navy to operate any fixed-wing aircraft with a maximum weight of over 3,300 lb (1,500 kg). Following a lengthy evaluation of the Sea Harrier and AV-8B, an order was placed for two TAV-8Bs in May 1989. Soon, a