The United States Army Air Corps developed the Boeing B-17 Flying Fortress in the 1930s. It was a four-engined heavy bomber. Boeing competed against Douglas and Martin for a contract to build 200 bombers. The Boeing entry outperformed both competitors and exceeded the air corps’ performance specifications.
Boeing lost the contract (to the Douglas B-18 Bolo) because the prototype crashed. Despite this, 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. Eventually, it became the third-most produced bomber of all time, behind the B-24 Liberator and the twin-engined Junkers Ju 88.
The B-17 was primarily employed by the United States Army Air Forces in the daylight strategic bombing campaign of World War II against German industrial and military targets.
The United States 8th Air Force was based at many airfields in England, whereas, the 15th Air Force was based in Italy. Both forces helped the RAF Bomber Command’s night-time area bombing. This was known as the Combined Bomber Offensive. Overall, this helped to secure air superiority over the cities, factories and battlefields of Western Europe in preparation for the invasion of France in 1944.
The B-17 also participated to a lesser extent in the War in the Pacific, early in World War II. Here, it conducted raids against Japanese shipping and airfields.
It inspired the making of two motion pictures. Firstly, a 1944 documentary film, Memphis Belle: A Story of a Flying Fortress. It then went on to inspire a 1990 Hollywood feature film, Memphis Belle.