B-17 Flying Fortress "Thunderbird"B 17 Thunderbird airplane model. The B 17G Flying Fortress evolved through continuous refinement of earlier models, transforming the legendary bomber into its ultimate form. While the distinctive Bendix chin turret is often recognized as the G model's signature feature, it actually appeared on late production F variants first. This definitive version was manufactured by an impressive industrial coalition of Boeing, Douglas, and Lockheed Vega, with