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 aircrew were given the task of flying a required number of operations, an "operational tour", usually of about 30 operations (missions in USAAF terminology). On completion of an operational tour the airman (and often his complete crew as they tended to remain very tight-knit, always flying together) would be "screened" (taken off operational flying) and split up as they received their future postings which would frequently be serving at Operational Training Units or Heavy Conversion Units preparing the next groups of young bomber crews for their postings to operational squadrons. Between March 1943 and the early summer of 1944 the