During the 1930s the United States fell behind other nations in the development of fighter aircraft. This was explained in part by the Army Air Corps’ concentration on developing long-range bombers. At the opening of the war the U.S. relied essentially on two fighter aircraft. Both the Bell P-39 “Aircobra” and Curtiss P-40 “Warhawk,” designed in the mid-1930s, were single-engine fighters. Each weighed about 4,000 pounds and had from four to six machine guns depending on the model. Between 1940 and 1944, when production ceased, a total of 9,558 P-39s and 13,738 P-40s had been accepted for service in the Army Air Forces. Only the P-40, which was employed with good success by Clair Chennault’s “Flying Tigers” in China during 1940-1942, received notoriety during the war.
The Army Air Forces developed three additional fighters that found service in the war. The Lockheed P-38 “Lightning,” with its unique forked-tail was designed in 1937 for high-altitude interception. A superior aircraft in terms of performance and firepower, comparing favorably with the British “Spitfire” and German ME-109, by Pearl Harbor the service had an inventory of only 69 P-38s. In all 9,536 P-38s were accepted for use in the Air Forces during the war and it found service in all theaters.
The Republic P-47 “Thunderbolt” was one of the most significant fighters of the war. By January 1944 approximately 40 percent of U.S. fighter groups serving overseas were equipped with it. Designed in 1940, the P-47 mounted six to eight 50-caliber machine guns and six 5-inch rockets. An excellent escort plane for bombers, it was also a superior ground attack aircraft. By May 1945 5,595 P-47s were in active service with the Army Air Forces in all theaters.
The last U.S. fighter that saw heavy service in World War II was the North American P-51 “Mustang,” the so-called “Cadillac of the skies.” Prior to the war many bomber enthusiasts had believed that their armadas would be invincible to attack from enemy fighters, a theory that was quickly dispelled during the strategic bombing campaign in Europe. Accordingly, fighters were employed as escorts for the bombers, but none had sufficient range to stay with the bomb groups over Germany. The P-51 was the direct result. It was designed initially for the British in 1940, with the Army Air Forces taking little interest until 1942. The first American group was equipped with P-51s in November 1943. It proved so successful in merging performance, range, and armament that by the end of the war 5,541 P-51 were in the Army Air Forces inventory. Along with the P-38 and P-47, the P-51 carried the brunt of the fighter mission for the Army Air Forces in all but the opening days of the war.