B-17

B-17 Flying Fortress
Boeing B-17E
Role	Heavy bomber
National origin	United States
Manufacturer	Boeing
First flight	28 July 1935
Introduction	April 1938
Retired	1968 (Brazilian Air Force)
Primary users	United States Army Air Forces Royal Air Force
Produced	1936–1945
Number built	12,731
Unit cost	US$238,329 (1945)
Variants	XB-38 Flying Fortress YB-40 Flying Fortress C-108 Flying Fortress
Developed into	Boeing 307 Stratoliner

The Boeing B-17 Flying Fortress is a four-engine 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 outperformed both competitors and exceeded the air corps' performance specifications. Although Boeing lost the contract 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.

The B-17 was primarily employed by the United States Army Air Forces (USAAF) in the daylight strategic bombing campaign of World War II against German industrial and military targets. The United States Eighth Air Force, based at many airfields in central and southern England, and the Fifteenth Air Force, based in Italy, complemented the RAF Bomber Command's nighttime area bombing in the Combined Bomber Offensive to help 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, where it conducted raids against Japanese shipping and airfields.

From its prewar inception, the USAAC (by June 1941, the USAAF) promoted the aircraft as a strategic weapon; it was a relatively fast, high-flying, long-range bomber with heavy defensive armament at the expense of bombload. It developed a reputation for toughness based upon stories and photos of badly damaged B-17s safely returning to base. The B-17 developed a reputation as an effective bomber, dropping more bombs than any other U.S. aircraft in World War II. Of the 1.5 million tonnes of bombs dropped on Germany and its occupied territories by U.S. aircraft, 640,000 tonnes were dropped from B-17s. In addition to its role as a bomber, the B-17 was also employed as a transport, antisubmarine aircraft, drone controller, and search-and-rescue aircraft.