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 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.