British Aerospace and Marconi Electronic Systems merge to form BAE Systems, Europe's largest defense contractor and the fourth largest aerospace firm in the world.

British Aerospace plc (BAe) was a British aircraft, munitions and defence-systems manufacturer that was formed in 1977. Its head office was at Warwick House in the Farnborough Aerospace Centre in Farnborough, Hampshire. It purchased Marconi Electronic Systems, the defence electronics and naval shipbuilding subsidiary of the General Electric Company, in 1999 to form BAE Systems.

Marconi Electronic Systems Limited (MES), or GEC-Marconi as it was until 1998, was the defence arm of General Electric Company (GEC). It was split off from GEC and bought by British Aerospace (BAe) on 30 November 1999 to form BAE Systems. GEC then renamed itself Marconi plc.

BAE Systems plc is a British multinational aerospace, arms and information security company, based in London. It is the largest manufacturer in Britain as of 2017. It is the largest defence contractor in Europe and the seventh largest in the world based on applicable 2021 revenues. Its largest operations are in the United Kingdom and in the United States, where its BAE Systems Inc. subsidiary is one of the six largest suppliers to the US Department of Defense. Its next biggest markets are Saudi Arabia, then Australia; other major markets include Canada, Japan, India, Turkey, Qatar, Oman and Sweden. The company was formed on 30 November 1999 by the £7.7 billion purchase of and merger of Marconi Electronic Systems (MES), the defence electronics and naval shipbuilding subsidiary of the General Electric Company plc (GEC), with British Aerospace, an aircraft, munitions and naval systems manufacturer.