In 1935, American Curtiss-Wright Corporation participated in the contest of fighter aircraft design proposed by the Army Air Corps with their Hawk Model 75. The contest was delayed due to accidents. The USAAC finally awarded P-35 designed by Seversky as new generation fighter aircraft.
However the productivity of P-35 was low. The US Army therefore asked Curtiss-Wright Corp. to test Hawk 75E powered by R-1830-13 engine. In July of 1937, Hawk 75E won an order for 210 aircrafts and designated as P-36A.
Some export version P-36' s with fixed landing gear were sold to China as soon as production completed. These fighters were entered combat against Japanese immediately. P-36 was also sold to France, Netherlands and Norway some time later. The US Army was not yet satisfied with P-36A s performance. So, Curtiss tried to improve furthermore by installing a more powerful Allison V-1710-19 liquid-cooled engine on P-36A. The new developed XP-40 made its first flight in October 1938, re-designed the radiator under the nose and landing gear hatch doors later. The US Army decided to order production model P-40 in April of 1939. As Curtiss had already expanded their plant for export model P-36 production, P-40 series was the only aircraft capable to serve in quantity when the United States entered the War, although its performance was so-so.
Because of P-40 performed inferior to other US aircrafts during the same period, Curtiss went on to improve it after the aircraft entered service with US Army. However, little they can do but upgrade the engine, adjust the armament or minor amendments on aerodynamics. P-40M that evolved from P-40K arrived in February 1943 as an urgent replacement for P-60, successor to P-40 but development was not succeeded. 600 of P-40M powered by Allison V-1710-81 were produced. Most of them were supplied to Soviet Union and the Commonwealth. Few of them were remained in the US Army for training purpose.