Nearly outdated by by the time the U.S. really entered the war, the P-40 was the U.S. front line fighter and saw extensive service in the Pacific, North Africa and China campaigns. One of my favorites since I was a kid, the P-40 is a very good aircraft, but was a bit slow for the newer enemy aircraft. The allison used, like in the P-51A, lacked the high-altitude performance needed.