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
Technology during World War II fighter planes. American bomber planes such as the B-17 Flying Fortress had been built before the war as the only adequate long-range bombers in the world, designed to patrol the long American coastlines. Defended by as many as six machine-gun turrets providing 360° cover, the B-17s were still vulnerable without fighter protection even when used in large formations. Despite the abilities of Allied bombers, though, Germany was not quickly crippled by Allied air raids. At the start of the war the vast majority of bombs fell miles from their targets, as poor navigation technology ensured that Allied airmen frequently could