With the outbreak of war in 1939, Kingstown's runways proved too short for the latest generation of larger multi-engined bombers and there was no room for runway expansions, so the RAF built and developed a new airfield at Crosby-on-Eden. The new facility came into operation in February 1941, the station designated as RAF Crosby on Eden which, following its wartime service, today serves as Carlisle Lake District Airport. RAF Kingstown was retained by the RAF, and converted to No 24 Elementary Flying Training School (EFTS).