This is the North American Aviation Valkyrie gigantic supersonic strategic nuclear bomber, that never entered service. There were only two prototypes built of the Valkyrie, before the project was cancelled. The supersonic bomber powered by six
cm FlaK 40 heavy anti-aircraft gun, one of the effective weapons of its type during WWII. Used to counter enemy bomber raids. Outcome of fighters and bombers being shot down by this created better armor designs for future planes.