Boeing XB-38 Flying Fortress The XB-38 was destroyed and the project was canceled, in part because the V-1710 engines were needed for other projects such as the Lockheed P-38 Lightning, Bell P-39 Airacobra, Curtiss P-40 Warhawk, North American P-51A Mustang, and Bell P-63 Kingcobra fighters. Boeing XB-38 Flying Fortress The XB-38 Flying Fortress was a single example conversion of a production B-17E Flying Fortress, testing whether the Allison V-1710 V type engine could be substituted for the standard Wright R-1820 radial engine during early World War II. The XB-38 was the result of a modification project undertaken by Boeing and Vega (a subsidiary of
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.