P-40 Warhawk aircraft

The P-40 Warhawk was developed by Curtiss from the older P-36 Hawk fighter aircraft. The P-36 of the 1930s used a radial engine, this was replaced with the new inline V12 engine manufactured by Allison, the V-1710 producing around 1,040 hp in it's early form.
The fighter first flew in October 1938 and it was received well enough for production orders to be placed, first deliveries going to USAAC (as the USAAF was then still called) squadrons.

The British soon got hold of the P-40, this being caused by the fall of France, who had ordered some of the aircraft. These machines were diverted to Britain and christened the Tomahawk 1. It was not a particularly popular type with the British at this point however, and was mostly used as a recce aircraft. This was mainly due to the aircraft's Allison engine running out of puff at the altitude where most air to air action was taking place over Britiain, the channel and France. The climb rate was also rather poor compared with the other types the RAF had on hand at this time.
Around this time though the aircraft was being used with some success by the US volunteer pilots (the 'Flying Tigers') over in China where they were engaging the Japanese.

The P-40 design was being upgraded and modified for most of WW2, with engine power upgrades, armament changes, airframe changes and equipment upgrades. These were all called Warhawks when in US service but the British changed the name to Kittyhawk for the P-40D and later variants. The P-40D had a more powerful Allison engine, some fuselage modifications and could be used a as fighter-bomber aircraft, all of this making the plane more satisfactory to the RAF, where they were widely operated in the desert theatre.

Many other nations have operated the P-40, as well as the British and Americans the Free French operated the P-40, as did the Russians who received various different marks of the aircraft. Some later Warhawks were even fitted out with licence built Packard Merlin engines to achieve better performance. P-40 Warhawk production ended around the end of 1944.

P-40E Warhawk being evaluated

Aircraft pictures courtesy USAF top picture and NASA lower picture.