The 864,000 aircraft produced during WWII fell into three major categories: 39% were fighters, 32% were bombers and other air-to-ground combat aircraft, while the remainding 29% were non-combat aircraft such as trainers, reconnaissance aircraft and transports. As figure 6 shows, the balance between these three categories varied significantly by country reflecting differences in circumstances and strategy.

Two features of the production mix stand out. The first is that the Axis powers produced a much larger proportion of fighters than bombers, while the Allies produced fighters and bombers in roughly equal numbers. The second is that the western Allies produced a much greater proportion of non-combat aircraft than either the Axis powers or the USSR.

Overall the US, like all three major Allied aircraft producers, build roughly the same number of fighters as bombers. However, the fighter total included a much smaller proportion of defensive fighters than was the case for the other major producers. The US had a relatively low need for defensive fighters because most of its territory was beyond the reach of its adversaries, although it still needed some defensive fighters to protect its outlying territories, military bases and fleets. Meanwhile, large numbers of other types of fighter were built. The US invested heavily in escort fighters for its bombers, and also produced large numbers of fighter-bombers, being an early convert to using them in place of light bombers.

On the bomber side of the equation the US built very large numbers of heavy strategic bombers to support its massive bombing campaigns in both European and Pacific theatres. The US also built large numbers of medium bombers and maritime patrol aircraft, many of which were exported to other Allies. Although there was close parity in the number of fighters and bombers built, by far the larger share of resources was devoted to bombers on account of their greater size and complexity.

The most distinctive feature of the US production mix was that the country produced a much larger proportion of non-combat aircraft than any other major producer: they accounted for 38% of US production compared to about 25% for all other countries combined. Even in Great Britain non-combat aircraft accounted for only 28% of production.

The biggest contributor to this very large number of non-combat aircraft was training aircraft ­ the US produced well over 40% of all training aircraft built during the war. The US air arms had massive training requirements as they expanded from their small pre-war size to become the world’s largest. Moreover, the US air arms operated many aircraft with large crews, creating a substantial need for crew training in addition to pilot training. And beyond their own training requirements the US also exported training aircraft to British and Commonwealth air forces, as well as providing them with aircrew training in the US. From November 1940 to February 1943 trainers accounted for more than half the USAAF inventory.

A second smaller factor was the large production of transport aircraft in the US. While all combatants produced transport aircraft in small numbers, the US alone produced many thousands of them, including more than three quarters of heavy transports, of which the immortal C-47 Dakota was the most numerous.

Although Britain, like the US, built fighters and bombers in similar numbers, the mix of subcategories was different, although one common characteristic was a major emphasis on heavy strategic bombers. British production reflected a strong polarization between strategic bombers on the one hand, and defensive fighters on the other. Although Britain produced significant numbers of light and medium bombers in the first couple of years of the war, their use declined thereafter, partly because of growing use of fighter-bombers and partly because and most of the light and medium bombers that were used in the second half of the war were American in origin. A notable exception was the Mosquito which, unlike most light and medium bombers, was used primarily in a strategic role. Along with strategic bombers, Britain also produced maritime patrol aircraft, although this is another area where British forces predominantly used American aircraft.

The proportion of non-combat aircraft was second highest after the US, and would have been higher still were it not for the large number of training aircraft built in Canada, where many British aircrews conducted part of their training. Britain produced only a small number of transport aircraft, but built relatively large numbers of dedicated target tugs and other support types, while most other countries used old combat aircraft for the same purposes.

Like the US and Great Britain the USSR built fighters and bombers in roughly equal numbers, but the reasons were quite different. The USSR continued to use single-engiend attack aircraft for ground attack purposes long after the western Allies and Germany had switched to fighter bombers, in part because fighter bombers needed engines with a very high power-to-weight ratio, and the USSR lagged in engine technology. The Il-2 Stormovick, a dedicated ground attack and anti-tank aircraft, was the most produced aircraft if WWII, and accounted for well over half of Soviet aircraft in the bomber category, while toghether with its successor the Il-10, the Stormovik accounted for around two thirds of Soviet bomber production. Meanwhile the USSR also built substantial numbers of light and medium bombers, but only a handful of strategic bombers and maritime patrol aircraft.

While the relative proportion of fighters and bombers was close to that of the other Allies, the proportion of non-combat in Soviet production was closer to the Axis powers. Needs for training aircraft were lower than for the western Allies becasue the USSR started with a very large pool of trained aircrew and because most Soviet aircraft were single or two seat aircraft that operated mainly by day. Day fighters and ground-attack aircraft have lower traing requirements than night fighters or strategic bombers because they have small crews, and because they don't require extensive training in blind flying. The USSR also built relatively small numbers of transports and other categories of non-combat aircraft.

Japan was intermediate between Germany and the Allies in terms of its aircraft mix. While the Japanese did not build heavy strategic bombers, they did build large numbers of light and medium bombers for ground attack, interdiction and anti-shipping purposes. As in the case of the USSR, Japan lagged in engine development and was slow to switch to fighter bombers because its fighters were too light to carry a bomb load comparable with dedicated bombers. Overall the number of fighters exceeded that of bombers because in the second half of the war the country was forced on the defensive and build growing nmumbers of fighters for defensive purposes.

While the proportion of non-combat aircraft was higher than for Germany, it was lower than for other major combatants, and comprised almost entirely of training aircraft. And unlike Germany, Japan had not built large numbers of trainers during the 1930s. This reflected the relatively small scale of Japanese training programs; shortage of trained crews were to become a major problem as the war progressed.

Germany produced by far the largest proportion of fighter aircraft, and also the smallest proportion of non-combat aircraft of any major combatant.

The fact that the number of non-combat aircraft is relatively small is a direct reflection of the number of trainers produced. This was low for several reasons. Firstly, most German production during the second half of the 1930s was of trainers, and many of these soldiered on for much of the war. Secondly, Germany had a high proportion of single seat aircraft and few large aircraft and therefore had a much lower need for crew training than did the Western Allies. Thirdly, German trainer production was supplemented by production in countries such as Czechoslovakia, who weren’t trusted or competent to build combat aircraft. Fourthly, the number of hours spent training each pilot was reduced in the second half of the war as the Luftwaffe struggled to keep up pilot numbers.

Combat aircraft were heavily weighted towards fighters because from 1943 on Germany was under heavy and almost continuous assault by heavy bombers by both day and night and needed protection against them. So precisely as overall production reached its peak the German need for defensive fighters was its greatest. Also, the Germans fully embraced the trend towards fighter-bombers as the primary ground-attack platform, and so shifted production away from ground attack aircraft to fighter-bombers relatively early in the war.

Around 500 types of aircrraft were produced in quantity during World War II, and many more were produced only as prototypes. Of these, 300 types were produced in quantities of 100 or greater. But production was more concentrated than these figures imply: the top 100 powered types, listed in figure 7 below, accounted for 85% of production, and the top 25 accounted for half of all aircraft built.