Royal Air Force Coningsby or RAF Coningsby , is a Royal Air Force (RAF) station located south-west of Horncastle, and north-west of Boston, in the East Lindsey district of Lincolnshire, England. It is a Main Operating Base of the RAF and home to three front-line Eurofighter Typhoon FGR4 units, No. 3 Squadron, No. 11 Squadron and No. 12 Squadron. In support of front-line units, No. 29 Squadron is the Typhoon Operational Conversion Unit and No. 41 Squadron is the Typhoon Test and Evaluation Squadron. Coningsby is also the home of the Battle of Britain Memorial Flight (BBMF) which operates a variety of historic RAF aircraft. Plans for an airfield at Coningsby began in 1937 as part of the RAF's expansion plan. However progress in the compulsory purchase of the land was slow and delayed the start of work for two years. The station opened during the Second World War on 4 November 1940 under No. 5 Group, part of RAF Bomber Command. The first flying unit, No. 106 Squadron with the Handley Page Hampden medium bomber, arrived in February 1941, with active operations taking place the following month when four Hampdens bombed Cologne in Germany. The squadron was joined in April 1941 by No. 97 Squadron equipped with Avro Manchester medium bombers. In May 1942, aircraft from Coningsby participated in the 'Thousand Bomber' raid on Cologne. The original grass runways were found to be unsuitable for heavy bomber operations so the station was closed for nearly a year between September 1942 and August 1943, whilst paved runways were laid in preparation for accommodating such aircraft. At the same time further hangars were constructed. The first unit to return was the now-famous No. 617 'Dambusters' Squadron. Equipped with Avro Lancaster heavy bombers, the squadron was stationed at Coningsby from August 1943. Due to its specialist nature, the Dambusters carried out limited operations whilst at Coningsby, with the most notable being Operation Garlic, a failed raid targeting the Dortmund-Ems canal in Germany, when five out of the eight Lancasters on the mission failed to return home.