B-17 Flying Fortress units of the United States Army Air Forces 2d Bombardment Group, Langley Field, Virginia on 11 January 1936; the first production B-17B was delivered on 29 March 1939 also to the 2nd Bombardment Group. A total of 12,677 production Fortresses was built before production came to an end. In August 1944, the Boeing B-17 equipped no less than 33 overseas combat groups. The last Boeing-built B-17G was delivered to the USAAF on 13 April 1945. Following the end of World War II, the Flying Fortress was rapidly withdrawn from USAAF service, being replaced by the B-29 Superfortress. Literally thousands of Fortresses used in combat in Europe by Eighth
Boeing B-17 Flying Fortress British heavy bombers, the Avro Lancaster and Handley Page Halifax, dropped 608,612 long tons (681,645 short tons) and 224,207 long tons (251,112 short tons) respectively. The RAF entered World War II with no heavy bomber of its own in service; the biggest available were long-range medium bombers such as the Vickers Wellington, which could carry up to of bombs. While the Short Stirling and Handley Page Halifax became its primary bombers by 1941, in early 1940, the RAF entered into an agreement with the U.S. Army Air Corps to acquire 20 B-17Cs, which were given the service name Fortress I.