The prototype XP-39 first flew on 6 April 1938, and after several evaluation programs, some major modifications were made to the design, resulting in the first production version, the P-39C. This production version entered service with the US Army Air Corps in 1939, but was almost immediately upgraded to the P-39D model with self-sealing fuel tanks, more guns, and larger fuel capacity.
In July 1941, the Royal Air Force took delivery of the first of 675 P-39Ds (called the Model 14 by the RAF) which they had ordered the year before. Shortly after delivery, however, the RAF realized that the aircraft had minimal performance characteristics without a turbocharger, an accessory that had been deleted early in the aircraft’s development. It was too late to cancel the order, and only one RAF squadron (No. 601) ever flew it operationally. Over 250 of the others were sent to Russia, about 200 more were transferred to the US Army Air Force in Britain, and another 200 or so were sent back to America and designated as P-400s.
At least eight additional variants were later built. Most changes to the original design involved new engines and propellers, but otherwise the airframe remained very much the same over its production life. The P-39N and P-39Q were built for the Russian air force under the Lend-Lease military assistance program, and 4,773 Airacobras were delivered to Russia by American and Russian ferry pilots. Russian pilots appreciated the cannon-armed P-39 for its ground attack capability. Other P-39s served with Free French and British forces.
Seven P-39s were designated as the F2L and used as US Navy target drones. The Airacobra served successfully in the ground-attack role in North Africa, and in the Pacific theater, until more powerful fighters began replacing it in 1944. The Airacobra, though hampered by its lack of a turbocharger, was a very satisfactory low-altitude attack airplane, and served as faithfully as any other combat aircraft.
Wartime Service
The Airacobra saw combat throughout the world, particularly in the Southwest Pacific, Mediterranean and Russian theaters. Because its engine was not equipped with a supercharger, the P-39 performed best below 17,000 feet altitude. It often was used at lower altitudes for such missions as ground strafing.