Between 1939 and 1945 the combatants in World War II built about 864,000 aircraft - well over half of all the aircraft that have ever been produced. The rate of production accelerated as the war progressed, with all five major producers reaching their peak in 1944. Measured in terms of the number of aircraft built, 1944 production was 1.8 times that of 1942 and 5.8 times that of 1939. Production in all countries declined in 1945 - for the Axis powers because much of their capacity was destroyed, and for the Allies because output was rapidly scaled back as the war drew to a close.

About 70% of the 860,000 aircraft produced were combat aircraft such as fighters and bombers, while the remaining 30% were non-combat aircraft such as trainers, transports and reconnaissance aircraft. Among the combat aircraft, the largest category was fighters, which accounted for about 40% of the total. While by definition all of the 334,000 fighters built were designed for offensive air-to-air combat, many were fighter-bombers that combined an air-to-ground role with their air-to-air capabilities. Fighter-bombers cannot easily be separated from fighters since by the second half of the war the vast majority of fighters could also operate in an air-to-ground capacity when required. While the majority of fighters were single-engined, about 41,000 were twin-engined machines, many of which were dedicated to night operations.

Combat aircraft other than fighters - i.e. those designed primarily for air-to-ground operations - accounted for about 30% of total production. Most of the 275,000 aircraft in this category were bombers, ranging from short range single-engined dive-bombers to long range four-engined strategic bombers. Also included are cannon-equipped ground-attack aircraft, and army co-operation and maritime patrol aircraft that qualify as combat aircraft because, while their primary mission was reconnaissance, they could be equipped to attack the enemy ships and submarines they encountered.

World War II saw a dramatic advance in aviation technology from the fabric-and-wire biplanes of the 1930s to the first generation of jets. About 7.5% of the 860,000 aircraft produced during World War II were biplanes. Most of these were primary trainers, but several types of biplane combat aircraft were manufactured, especially during the first two years of the war, and biplane combat aircraft accounted for just over 1% of total production. At the other technological extreme, only about 4000 jet and rocket-powered aircraft were produced, accounting for less than 0.5% of the total.

Figure 1 shows how the total aircraft production was distributed among the combatants. It highlights the massive production advantage enjoyed by the Allies, who out-produced the Axis in every year of the war. As figure 2 shows, the imbalance in the Allies' favor increasing as the war progressed. During the entire seven year period the Allies produced about three times as many aircraft as the Axis, and the US alone accounted for nearly 40% of all aircraft produced. This imbalance in favor of the Allies was a major factor in their eventual victory.

Figure 3 shows an estimate for production for each country (or group of countries) from 1935 to 1945. Data for the earlier years reflects the varying speed at which rearmament got under way in each country. In most countries the pace was driven by the demands of their own armed forces, but the US differed in that the early stages of its production ramp were in response to orders from British and French purchasing missions in 1938 and 1939. The US did not start a major build-up of its own air arms until 1940.

Although figures 1 to 3 show a substantial production advantage in favor of the Allies, they actually understate the degree to which the Allies - and in particular the Americans - outperformed the Axis. The aircraft produced by the Allies were, on average, heavier and more powerful than those of their opponents and consumed correspondingly greater resources. Figure 4 shows production in terms of airframe weight rather than number of aircraft. By this measure the Allies accounted for nearly 80% of production, and the US alone accounted for nearly half.

The gap between the average sizes of aircraft produced by the two sides widened as the war progressed. A contributory factor was the differences in the air strategy of the two sides. While all major combatants started the war with a similar mix of fighters and light and medium bombers, the Western Allies pursued a strategic bombing campaign, and shifted a growing share of their production to heavy four-engined bombers. Each heavy bomber was equivalent in production terms to four or more single-engined aircraft. Meanwhile, forced on the defensive, the Axis powers, and in particular the Germans, shifted their production mix in the other direction towards a larger proportion of single-engined fighters. Had the Allies chosen to produce a similar mix of combat aircraft as the Axis, their production totals would certainly have been much higher.