Description The Boeing B-17 Flying Fortress was a four-engine heavy bomber aircraft developed for the United States Army Air Corps (USAAC) introduced in the 1930s. The B-17 was primarily employed by the United States Army Air Forces (USAAF) in the daylight precision strategic bombing campaign of World War II against German industrial, civilian, and military targets. The United States Eighth Air Force based in England and the Fifteenth Air Force based in Italy complemented the RAF Bomber Commands nighttime area bombing runs. With a service ceiling greater than any of its Allied contemporaries, the B-17 established itself as a superb weapons system, dropping more bombs than any other U.S. aircraft in World War II. Of the 1.5 million metric tons of bombs dropped on Germany by U.S. aircraft, 640,000 tons were dropped from B-17s. Shown here are Liberty Belle (left) and Thunderbird. They are two of only 8 surviving flyable B-17s left in the world.