Q: The P-51 Mustang is one of the most successful and famous warplanes of all time with over 15,000 built. What was the North American Aviation designation for the initial prototype which eventually became the P-51 Mustang?
Please post your answers in the comment section. The correct answer will be posted in one week.
Was it the NA-73X? 
Was that the XP-51? Actually, this was a designation assigned when it came to America. Prior to that I think it was the NA-73. I think that was the ID when it was sent to England. Not totally certain though. Good question for a great plane.
Both Laura and Emilie are correct. Both the NA-73X and XP-51 were prototypes however the NA-73X was the first or initial prototype. The XP-51 came later and both led to what would become one of the most famous fighter aircraft of all time, the P-51 Mustang
