<p>The pace of the build-up before World War II was unique, and outran even the frantic requirements of World War I. Within a very few years, the United States went from a fifth-rate air power to a first-rate one. But it started from a very low point. At the end of 1938, the first-line strength of the Army Air Corps stood at fewer than 500 airplanes. By late 1939, it was about 800. In September that year, the AAC had a total bomber force of 23 B-17 models of two types. About 700 of the first-line aircraft were one of three types: the Douglas B-18A, of which 350 were produced; the Northrop A-17A, with 239 built; and the Curtiss P-36A, with 243 produced. All were outdated.
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<p>In spite of major efforts by the AAC and by industry, the strength of the air arm did not significantly increase but, in fact, decreased as the war drew nearer. In the summer of 1941, with war less than six months away, the striking arm of the GHQAF included two groups of heavy bombers with a total of 70 planes; two groups with 114 medium bombers total; two groups of light bombers with the same strength; and three pursuit groups with a total of 225 aircraft. The numbers added to 523, the entire usable, operational fighting strength of the US Army Air Corps. No wonder that Major General Henry H. Arnold, Chief of the Air Corps, said that the Corps was at "zero strength."
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<p>There was one contributing factor that subtracted strength from the US forces: the delivery of large numbers of warplanes to France and Great Britain. The involvement of those countries in the American aircraft production build-up, and the subsequent influence of their purchases on production, is a major part of Air Corps history.
