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.

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

MES exists today as BAE Systems Electronics Limited, a subsidiary of BAE Systems, but the assets were rearranged elsewhere within that company. MES-related businesses include BAE Systems Submarine Solutions, BAE Systems Surface Ships, BAE Systems Insyte and Selex ES (now a part of Leonardo S.p.A.).

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