De Havilland Propellers Limited was established as a division of De Havilland Aircraft in 1935 to manufacture variable pitch propellers under licence from the Hamilton Standard Company. In 1946 it was incorporated as a subsidiary company based at Hatfield, with a manufacturing facility in Lostock. In addition to the manufacture of propellers the company would work on missile projects from the late 1940s and would diversify into industrial equipment in the 1950s. This decade would also see the company begin work on the Blue Jay project, which became the Firestreak heat-seeking missile, and Blue Streak, both as a missile and later as part of the European satellite launch programme. In 1960 the company, along with its parent, would become part of the Hawker Siddeley Group and the decision was taken to merge De Havilland Propellers and the De Havilland Aircraft Company into a single entity. This was known as the de Havilland Aircraft Company and removed the need for de Havilland Holdings which ceased to function. The new join company would continue to operate independently inside the Hawker Siddeley Group until 1963 when a reorganisation transferred the missile and equipment interests that had been de Havilland Propellers into Hawker Siddeley Dynamics.

Hawker Siddeley Dynamics Limited (HSD) was a defence and electronics manufacturer formed on 1st July 1963 as part of a reorganisation within the Hawker Siddeley Group. The new company was a consolidation of the missile and equipment interests of De Havilland, Whitworth Gloster and A.V. Roe, all of which had previously operated separately within the Group. The new establishment consisted of over 15,000 staff, headed by Sir Arnold Hall as chairman, operating on sites at Hatfield, Lostock, Farnworth, Lakefield, Stevenage, Welkin House, Conquest House, Woodford, Whitely, Spadeadam and Woomera. It would take over all of the projects these companies were involved in including the Firestreak, Blue Streak, Red Top, Blue Steel, Seaslug and CF.299 missiles, and various air-conditioning, fuel control and power supply projects. It also continued as the British representative on the ELDO (European Launcher Development Organisation) project. In August 1964 the company was chosen to supply air-conditioning equipment to the Concorde project and also announced the development of the Sea Dart missile for the Royal Navy. In 1966 it would also announce a further missile project when the Martel was unveiled in cooperation with Engins Matra. Beyond these military projects, there was also a great deal of work in the civilian sector including the design of the suspension and brake system for British Rail’s prototype Advanced Passenger Train (APT), which was awarded to them in 1969. In 1977 the Aircraft and Ship Building Act created British Aerospace (BAe) and Hawker Siddeley Dynamics, along with Hawker Siddeley Aviation, the British Aircraft Corporation and Scottish Aviation, were merged into it. The none aviation aspects of Hawker Siddeley would continue as a separate company until 1991 when it was acquired by BTR.

British Aerospace, often abbreviated to BAe, was an aerospace and defence company formed on 29th April 1977. This was a result of the Aircraft and Shipbuilding Industries Act which merged the British Aircraft Corporation, Hawker Siddeley Aviation, Hawker Siddeley Dynamics and Scottish Aviation into a nationalised company. The new company controlled a large part of the British aviation industry and was the largest defence contractor in Europe. In 1979 the company joined the Airbus consortium, acquiring a 20% share. The British government had previously withdrawn from this project although Hawker Siddeley had continued to be involved as a contractor producing wings for their aircraft. In 1981 the company underwent a major restructuring. On 1st January the statutory corporation was transferred to a limited company and this was reregistered as British Aerospace PLC. It was then gradually privatised as 51.6% of the shares were sold to the public in February with the remaining 48.4% being sold in May 1985. Despite this the British government retained a single golden share that gave them the power to block foreign control of the company. Also during 1985 BAe would be the primary contractor for the Al-Yamamah arms deal. During the late 1980s British Aerospace would become involved in serval joint ventures and acquired a number of companies which diversified its operations away from aircraft manufacturing. The first of these was undertaken in cooperation with Alenia Aeronautica, Construcciones Aeronáuticas SA and DaimlerChrysler Aerospace AG to form Eurofighter GmBH which would go on to develop the Eurofighter Typhoon. During 1991 it would also form another joint venture with the Sema Group to form a naval defence company, BAeSEMA. The company would also acquire Royal Ordnance on 22nd April 1987, the Rover Group in 1988, Heckler and Koch in 1991 and 30% share in Hutchison Telecommunications. Despite the expansion undertaken during the 1980s BAe would begin to suffer some difficulties during the early 1990s as its property company struggled, Rover sales dropped and the British government undertook a defence spending review. As a result the decision was taken to divest the company of its non-aerospace or defence activities. As a result in 1993 BAE Corporate Jets Ltd and Arkansas Aerospace Inc were sold to Raytheon and in 1994 the Rover Group was sold to BMW whist British Aerospace Space Systems were sold to Matra Marconi Space. As well as this in 1998 it reduced its shareholding in Orange to 5% and acquired the UK operations of Siemens Plessey Systems from Siemens AG. By the late 1990s the consolidation of defence companies was becoming a major issues especially in Europe. The formation of Lockheed Martin and the merger of Boeing and McDonnell Douglas put serious pressure on European companies to consolidate their operations. Initially it was thought that BAe would merge with DaimlerChrysler Aerospace AG but this was put on hold when it emerged that GEC was selling its defence electronics business, Marconi Electronic Systems. It was believed that this may be acquired by an American company. As a result the decision was taken to merge this company with British Aerospace forming a company that was initially known as New British Aerospace. The new company would be formed on 30th November 1999 under the name BAE Systems.