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,
Military history of the United States during World War II Empire and Chinese forces in Burma and suffered many casualties. On 10 August 1944 the Marauders were consolidated into the 475th Infantry. The U.S. also had an adviser to Chiang Kai-shek and Joseph Stillwell. Units of the Tenth Air Force, Fourteenth Air Force, and Twentieth Air Force of the USAAF also served in the theatre, including the previously mentioned "Flying Tigers". Military history of the United States during World War II The military history of the United States in World War II covers the war against Germany, Italy, and Japan, starting with the 7 December 1941 attack on Pearl Harbor.