The NA-73X project that was contracted to North American Aviation saw the first prototype of what would become the P-51 Mustang roll out 117 days after the green light. The design would have taken a...
51 stands for the model of the Plane. The P stands for the series of planes example: P-40 P-47P-38P-51The number i dentifies the specific plane. Planes are also updated or improved, so they put in...