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
B-17 Flying Fortress units of the United States Army Air Forces harbor facilities and Axis naval targets on Crete and Benghazi, Libya through which Afrika Korps supplies were landed. The B-17s made a final raid against installations at Sousse, Tunisia before being taken out of front-line service with the arrival of newer B-24 and B-25 units from the United States. B-17 Flying Fortress units of the United States Army Air Forces This is a list of United States Army Air Forces B-17 Flying Fortress units of the United States Army Air Forces including variants and other historical information. Heavy bomber training organizations primarily under II Bomber Command in the United States