The B-17 Flying Fortress is a four-engine bomber that was used extensively by the United States during World War II. The plane was designed by The Boeing Company in 1934 to meet the Army’s request for a large, multiengine bomber. http://www.acepilots.com/planes/b17.html Originally designed for coastal defense, the first prototype flew on July 28, 1935. The plane acquired the name of “Flying Fortress” after Richard Williams, a writer for The Seattle Times, saw the aircraft for the first time.https://docs.google.com/viewer?url=http://www.airforce-magazine.com/MagazineArchive/Magazine%2520Documents/2006/February%25202006/0206classics.pdf&pli=1

Although fewer than 13,000 planes were built between Boeing, Douglas Aircraft Company, and Lockheed Martin, only half survived to see the end of the war. Once the war was over, the remaining planes were either scrapped or used as target practice during the 1950s and 1960s. http://www.boeing.com/history/boeing/b17.html

The B-17 Flying Fortress was modified regularly over the course of its service life. Although the first model had five .50 caliber machine guns, the last model to reach mass production, the B-17G, had 13 guns strategically placed around its fuselage. The aircraft's armor, tail size, and fuel-tanks were also upgraded over time. http://www.aviation-history.com/boeing/b17.html

The B-17 dropped more bombs during World War II than any other aircraft involved in the conflict. The B-17 Flying Fortress was the first bomber to fly missions in both the European and Japanese theaters of war. Seventeen B-17 crewmen have received the Congressional Medal of Honor, the highest military decoration awarded by the United States.https://docs.google.com/viewer?url=http://www.airforce-magazine.com/MagazineArchive/Magazine%2520Documents/2006/February%25202006/0206classics.pdf&pli=1