B-17 Flying Fortress Aluminum OvercastB 17 Aluminum Overcast model airplane. The B 17G was the culmination of ongoing improvements made to earlier models of the B 17. After incorporating modifications and upgrades into the design, the G model became the production version of the B 17F. Along with the Bendix chin turret, which was first used on later B 17Fs, there were over 8,500 Gs built by Boeing, Douglas, and Lockheed Vega. In total, more than 12,500 B 17s of all varieties were produced