The P-40 was a great aircraft in the early war. It easily outclassed most other aircraft in some ways except for a select few. I don't believe the P-40 gets enough credit for that. The main problem with the P-40 has been stated already and that is its failure to be upgraded so it could be more competative after 1943. The P-40 was only outclassed by the Spitfire barely and if one had to choose an existing Allied aircraft for 1940 to 1942 the P-40 was one of the best.