The Curtiss P-40 was an American single-engine, single-seat, all-metal fighter and ground attack aircraft that first flew in 1938. It was used in great numbers in World War II. The P-40 design was a modification of the previous P-36; this reduced development time and enabled a rapid entry into production and operational service. When production of the P-40 ceased, in November 1944, 13,738 had been built. They were used by the air forces of 28 nations and remained in front line service until the end of the war. Warhawk was the name the United States Army Air Corps adopted for all models, making it the official name in the United States for all P-40s.