The Boeing B-17 Flying Fortress is an American four-engine heavy bomber aircraft developed for the US Army Air Corps (USAAC). Competing against Douglas and Martin for a contract to build 200 planes, the Boeing entry outperformed both the other competitors and more than met the Air Corps' expectations. Although Boeing lost the contract due to the prototype's crash, the Air Corps was so impressed with Boeing's design that they ordered 13 B-17s. The B-17 Flying Fortress went on to enter full-scale production and was considered the first truly mass-produced large aircraft, eventually evolving through numerous design advancements, from B-17A to G.

The B-17 Aluminum Overcast

The Experimental Aircraft Association's B-17G-VE, serial number 44-85740 - nicknamed, Aluminum Overcast, was delivered to the U.S. Army Air Corps on May 18, 1945.  Although delivered too late to see action in World War II, the airplane has an interesting history.

Aluminum Overcast proudly carries the colors of the 398th Bomb Group of World War II, which flew hundreds of missions over Nazi-held territory during the war. Aluminum Overcast commemorates B-17G #42-102515 which was shot down on its 34th combat mission over Le Manior, France, on August 13, 1944. Veterans of the 398th helped finance the bomber's restoration.

http://www.b17.org/history/aluminum_overcast.asp

http://www.aviation-history.com/boeing/b17.html