Boeing B-17 Flying Fortress Boeing B-17 Flying Fortress The Boeing B-17 Flying Fortress is a four-engined heavy bomber developed in the 1930s for the United States Army Air Corps (USAAC). Competing against Douglas and Martin for a contract to build 200 bombers, the Boeing entry (prototype Model 299/XB-17) outperformed both competitors and exceeded the air corps' performance specifications. Although Boeing lost the contract (to the Douglas B-18 Bolo) because the prototype crashed, the air corps ordered 13 more B-17s for further evaluation. From its introduction in 1938, the B-17 Flying Fortress evolved through numerous design advances, becoming the third-most produced bomber of all time,
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,