The P-40 design was a modification of the previous Curtiss P-36 Hawk which reduced development time and enabled a rapid entry into production and operational service.

[6][N 1] The lack of a two-speed supercharger for the P-40's Allison V-1710 engine's made it inferior to Luftwaffe fighters such as the Messerschmitt Bf 109 or the Focke-Wulf Fw 190 in high-altitude combat and it was rarely used in operations in Northwest Europe.

[9] Based on war-time victory claims, over 200 Allied fighter pilots – from the UK, Australia, New Zealand, Canada, South Africa, the US and the Soviet Union – became aces flying the P-40.

[13] Without beneficial tail winds, Kelsey flew the XP-40 from Wright Field back to Curtiss's plant in Buffalo at an average speed of 354 mph (570 km/h).

At medium and high speeds it was one of the tightest-turning early monoplane designs of the war,[20] and it could out-turn most opponents it faced in North Africa and the Russian Front.

It lacked innovations such as boosted ailerons or automatic leading edge slats, but its strong structure included a five-spar wing, which enabled P-40s to pull high-G turns and survive some midair collisions.

[25] Operational range was good by early war standards and was almost double that of the Supermarine Spitfire or Messerschmitt Bf 109, although inferior to the Mitsubishi A6M Zero, Nakajima Ki-43 and Lockheed P-38 Lightning.

[9] I would evade being shot at accurately by pulling so much g-force...that you could feel the blood leaving the head and coming down over your eyes... And you would fly like that for as long as you could, knowing that if anyone was trying to get on your tail they were going through the same bleary vision that you had and you might get away...

[35][36][37] Against its lack of high-altitude performance, the P-40 was considered to be a stable gun platform and its rugged construction meant that it was able to operate from rough front line airstrips with a good rate of serviceability.

The first official victory occurred on 8 June, when Hamlyn and Flight Sergeant (Flt Sgt) Tom Paxton destroyed a CANT Z.1007 from 211a Squadriglia of the Regia Aeronautica, over Alexandria.

The superior climb rate of the Bf 109 enabled fast, swooping attacks, neutralizing the advantages offered by conventional defensive tactics.

[40] Werner Schröer, who was credited with destroying 114 Allied aircraft in only 197 combat missions, referred to the latter formation as "bunches of grapes", because he found them so easy to pick off.

[45] The Flying Tigers, known officially as the 1st American Volunteer Group (AVG), were a unit of the Chinese Air Force, recruited from amongst U.S. Navy, Marine Corps and Army aviators and ground crew.

"Scores of new planes...were now in India, and there they stayed—in case the Japanese decided to invade... the AVG was lucky to get a few tires and spark plugs with which to carry on its daily war.

[48][57][58] As was also the case with the Bell P-39 Airacobra, many USAAF officers considered the P-40 exceptional but it was gradually replaced by the Lockheed P-38 Lightning, the Republic P-47 Thunderbolt and the North American P-51 Mustang.

At Pearl Harbor[59] and in the Philippines,[60] USAAF P-40 squadrons suffered crippling losses on the ground and in the air to Japanese fighters such as the A6M Zero and Ki-43 Hayabusa respectively.

Robert DeHaven describes how this tactic was used in the 49th Fighter group: USAAF and Chinese P-40 pilots performed well in this theater against many Japanese types such as the Ki-43, Nakajima Ki-44 "Tojo" and the Zero.

[65] Units arriving in the CBI after the AVG in the 10th and 14th Air Forces continued to perform well with the P-40, claiming 973 kills in the theater, or 64.8 percent of all enemy aircraft shot down.

2nd Lt Joseph D. Shaffer, of the 33rd Fighter Squadron, intercepted a Focke-Wulf Fw 200C-3 maritime patrol aircraft that overflew his base at Reykjavík, Iceland.

Decoded Ultra signals revealed a plan for a large formation of Junkers Ju 52 transports to cross the Mediterranean, escorted by German and Italian fighters.

On 22 April, in Operation Flax, a similar force of P-40s attacked a formation of 14 Messerschmitt Me 323 Gigant ("Giant") six-engine transports, covered by seven Bf 109s from II./JG 27.

In the brief, intense battle that occurred ... [the 317th claimed] 21 enemy aircraft.Cathcart wrote that Lt. Robert Sederberg assisted a comrade being attacked by five Bf 109s, destroyed at least one German aircraft, and may have shot down as many as five.

"[75] At the same time as the heaviest fighting in North Africa, the Pacific War was also in its early stages, and RAAF units in Australia were completely lacking in suitable fighter aircraft.

USAAF P-40s and their pilots originally intended for the U.S. Far East Air Force in the Philippines, but diverted to Australia as a result of Japanese naval activity were the first suitable fighter aircraft to arrive in substantial numbers.

They fought on the front line as fighters during the critical early years of the Pacific War, and the durability and bomb-carrying abilities (1,000 lb/454 kg) of the P-40 also made it ideal for the ground attack role.

[76] General Henry H. Arnold said of No 75 squadron: "Victory in the entire air war against Japan can be traced back to the actions which took place from that dusty strip at Port Moresby in early 1942.

During a major attack on Japanese positions at Kiska on 25 September 1942, Squadron Leader Ken Boomer shot down a Nakajima A6M2-N ("Rufe") seaplane.

In January 1943, a further Article XV unit, 430 Squadron was formed at RAF Hartford Bridge, England and trained on obsolete Tomahawk IIA.

[24] The Tomahawks were shipped from Great Britain and directly from the US, many of them arriving incomplete, lacking machine guns and even the lower half of the engine cowling.

VVS pilots usually flew the P-40 at War Emergency Power settings while in combat, which brought acceleration and speed performance closer to that of their German rivals, but could burn out engines in a matter of weeks.