It began as a modified version of the P-36 Hawk, an aircraft that Curtiss had previously built. It was equipped with a single engine (normally an Allison V-1710 V-12[N 1]), two .50 in (12.7 mm) machine guns in the nose, and two .303 Browning machine guns on each wing. Later versions, however, would have three .50 in (12.7 mm) guns in each wing. The P-40 was produced until November 1944, and was used in the air forces of 28 nations, including Great Britain.
Development began with the XP-40, which was the 10th production example of the P-36. This was fitted with an Allison V-1710-19 (C-13) inline engine, under the terms of a USAC order dated 30 July 1938. The type's first flight on 14 October 1938 revealed a lack of speed, which was resolved by moving the radiator from the belly to the underside of the engine cowling. This increased top speed from 299 mph (481 km/h) to 342 mph (550 km/h). and resulted in the placing of an order for 524 production examples on 27 April 1939. The first of these, powered by a V-1710-33 (C-15) and fitted with a pair of fuselage mounted Browning M2 Machine Guns, made its initial flight on 4 April 1940, and was followed by another 198 P-40s. These were followed by 131 P-40Bs with pilot armour, self-sealing fuel tanks and a 0.3 in guns in each wing, and led to the P-40C, which was basically a P-40B with an additional 0.3 in gun in each wing.
These were followed by the P-40D (Hawk 87A-2), fitted with a new series of Allison engine, resulting in a shorter nose and deeper radiator housing. The fuselage mounted guns were deleted, with armament being standardised as six 0.5 in M2 Machine Guns mounted in the wings. The similar P-40E (Hawk 87A-3), which primarily differed in having the P-40D's cannon provision deleted, became the first P-40 variant built in large numbers after the Bombing of Pearl Harbor, with 2,320 built on American contracts, supplemented by 1,500 built for the RAF as the Kittyhawk Mk IA.
A number of captured P-40Es were used by the 50 Hiko Sentai of the IJAAF to defend Japanese occupied Rangoon during 1943. On 21 March 1943 a combination of factors resulted in a number of Mitsubishi Ki-21 bombers, which were returning from an attack against Feni Airfield, being shot down by Japanese flown P-40s operating from Mingaladon.
- Bingham, Victor. Merlin Power - The Growl Behind Air Power in World War II. Airlife Publishing Ltd. 1998. ISBN 1 85310 068 4 Page 162
- Scale Aviation Modeller International. SAM Publications. Feb 2002 Page 146
- SAMI Feb 2002 Page 139
- Green, William and Gordon Swanborough. Complete Book of Fighters. Salamander Books. 2001. ISBN 1-84065-269-1 Page 138
- Template:Illustrated World War II Fighting Aircraft Directory Page 112
- World Aircraft Information Files Aviation Partwork. Midsummer Books Ltd. File 69 Sheet 2 (World Military Aircraft:Curtiss P-40 Warhawk Family - P-40 Variants)
- WAIF File 69 Sheet 1 (World Military Aircraft:Curtiss P-40 Warhawk Family - Introduction)
- Japanese Aircraft