Boeing B-17 Flying Fortress

The Boeing B-17 Flying Fortress is an American four-engined heavy bomber aircraft developed in the 1930s for the United States Army Air Corps. A fast and high-flying bomber of its era, the B-17 was used primarily in the European Theater of Operations and dropped more bombs than any other aircraft during World War II. It is the third-most produced bomber of all time, behind the American four-engined Consolidated B-24 Liberator and the German multirole, twin-engined Junkers Ju 88. It was also employed as a transport, antisubmarine aircraft, drone controller, and search-and-rescue aircraft.

In a USAAC competition, Boeing's prototype Model 299/XB-17 outperformed two other entries but crashed, losing the initial 200-bomber contract to the Douglas B-18 Bolo. Still, the Air Corps ordered 13 more B-17s for further evaluation, which were introduced into service in 1938.

Source: Wikipedia