Boeing YB-40 Flying Fortress Boeing YB-40 Flying Fortress The Boeing YB-40 Flying Fortress was a modification for operational testing purposes of the B-17 Flying Fortress bomber aircraft, converted to act as a heavily armed gunship for other bombers during World War II. At the time of its development, long-range fighter aircraft such as the North American P-51 Mustang were just entering quantity production, and thus were not yet available to accompany bombers all the way from England to Germany and back. Work on the prototype, Project V-139, began in September 1942 by converting the second production B-17F-1-BO (serial number 41-24341) built. Conversion work was
RAF Bomber Command aircrew of World War II air gunner to man the mid-upper gun turret although sometimes the gunners would agree to exchange turrets. At the outbreak of war in September 1939 operational Royal Air Force bomber squadrons in Europe were equipped with two main categories of bombers, single-engined Fairey Battle and twin-engined Bristol Blenheim light bombers and Armstrong Whitworth Whitley, Vickers Wellington and Handley Page Hampden medium bombers. Bomber Command aircrew "trades" flying operationally in the early stages of the war were: Pilot – A qualified pilot flew the aircraft and in the Royal Air Force was usually the captain (function not rank) of the crew,