According to sources such as Paul Kennedy's "The Rise and Fall of the Great Powers, America's total armaments spending in 1941 was about half that of the Axis (Germany, Italy and Japan). It was also less than Britain's military spending, which was equivalent to Germany's alone, and Russia's, which was equivalent to that of Germany plus Japan.

Yet by 1941, America produced 26,000 planes, more than either Britain or Russia (singly), as well as all the Axis nations combined. Put another way, the 1941 base was so high that U.S. aircraft production rose "only" threefold from 1941-1943, versus eightfold for total armaments spending.

Why was U.S. aircraft production already superior to that of both allies and enemies in 1941 when the country only had something like a million men in the Army (about as many as prewar Poland), and e.g. a merchant marine production that grew eightfold (in line with armaments, rather than aircraft spending) over the next two years? Was the air force more "hawkish" than other branches of the service? Or was air defense considered more critical than ground forces?

  • does he say which types of planes made up that 26k? were maybe some of those planes commercial or being built for other countries?
    – ed.hank
    Feb 23, 2020 at 18:40
  • 2
    Per wikipedia: "In 1939 there were only 55 enlisted pilots in the then-U.S. Army Air Corps (USAAC)." Does not sound like a good preparation for the air war. Feb 23, 2020 at 19:07
  • 3
    @MoisheKohan's comment is a little misleading, as most AAC pilots of the time were officers, not enlisted men. I don't know how many pilots the AAC had in 1939, but it was more than 55. Of course M K is right that they might have had more eniisted pilots then, if they had really wanted them. Feb 23, 2020 at 19:56
  • @MoisheKohan: By 1941, there were plenty of other pilots besides the U.S Army Air Corps. For instance, there were hundreds of naval pilots (and airplanes) that won us the battles of Coral Sea and Midway early in 1942.Also, 1939 is not 1941. There was a steep gradient in American air preparedness between 1939-1941. The whole point of the question is why did the American air power ramp up in those years while the other part did so from 1941-1943.
    – Tom Au
    Feb 24, 2020 at 1:00
  • The Wikipedia article on WWII US aircraft production has considerably different numbers than you quote. Also prior to the US entry into the war, many aircraft were produced under contract for Britain & France. en.wikipedia.org/wiki/…
    – jamesqf
    Feb 24, 2020 at 3:25

4 Answers 4


Why the big change in aircraft production 1939 to 1941?


I know that sounds over-simplified, but it in 1939 was obvious that the world was at war again, and even though the war was in Europe, it still had to be considered as a threat to US security, to the security of the western hemisphere as defined by the policies of the Monroe Doctrine.

Why make Aircraft

A book from 1948, The Army Air Forces in World War II: Plans and early operations, January 1939 to August 1942, published by the Office of Air Force History has quite a bit to say about this development phase, and the reasons why it took pace. (all following emphasis mine, web page for the information here

When war broke out in Europe in September 1939, the United States declared its neutrality.4 Its stated policy was to remain out of the conflict if possible and at the same time to keep the totalitarian powers out of the Western Hemisphere. The latter objective demanded a further extension and an acceleration of previous programs for strengthening American armed forces. It called also, because of the threat of new weapons and modes of warfare, for the establishment of new strategic bases. The declared policy was wholly consonant with the Monroe Doctrine, and the measures taken to enforce it were, for a while, consistent with our traditional ideas of defense.

From Sept 1939 on, there was an understanding that, even if we could maintain neutrality, air power was going to play a strong role in this new conflict. We had the advantage of observing this, and reacted accordingly.

The new concept was influenced by the military techniques of the Nazis as well as by their unbroken string of victories. The pattern of political infiltration, violent air attack, and machine-like blitzkrieg encouraged the conviction that defense of the Western Hemisphere was closely linked with the survival of the Allies, especially of England: an Allied victory would forestall an Axis invasion of the Americas and even by merely prolonging Allied resistance the United States would gain time needed for building its defenses. So in 1940 aid to the Allies had become the avowed policy of the American government.

So, we see an understanding that war could spill over to this hemisphere, and that the best defense we had at the time was the survival of the UK. Steps were taken to develop a strategy to maintain our security:

Preparations initiated by the United States government in the period 1939-41 involved, then, four interrelated activities: expansion of the military establishment; development of a new doctrine of hemisphere defense; aid to the Allies; and the formulation of strategic war plans. To an important degree the nature of those defense measures was determined by the nature of the conflict in Europe. Thus in light of the vital role played by the air arm in German offense and in British defense, it was natural that the United States should place great emphasis on the development of air power. And hence during the period 1939-41 the Air Corps figured prominently in each of the four aspects

During the time of the buildup in this question, the Battle of Britain takes place. This put any doubts concerning the necessity of advancing the concept of air power as being vital to a nations defense. The UK was fighting for its very existence, and there were no ships, no tanks, no infantry soldiers involved in the fight (metaphorically speaking). Air Power.

Now since the title line question asks why this occurred, I'll stop here. The cited book does continue with much more information concerning how this expansion took place. In the desire to not copy an entire chapter from a book, I'll stop here for now.

How did we increase Production so quickly?

Ok. A little on the how, and the numbers involved (still from the same source above)

The presidential message to Congress of 12 January 1939 marked the beginning of a period of Air Corps expansion which did not reach its peak until 1944. Asserting that "increased range, increased speed, increased capacity of airplanes abroad have changed our requirement for defensive action," President Roosevelt strongly urged that $300,000,000 be appropriated for the purchase of aircraft for the Army.6 The existing force, which the President described as "utterly inadequate," consisted of approximately 1,700 tactical and training planes, some 1,600 Air Corps officers, and 18,000 enlisted men.7 Within three months Congress had passed an emergency Army air defense bill substantially as requested, authorizing the procurement of 3,251 aircraft. This act approved a total Air Corps strength of 5,500 planes, 3,203 officers, and 45,000 enlisted men. The appropriation amounted to half as much as the Air Corps had received in the fourteen preceding fiscal years;8 approved strength for officers was doubled, for enlisted men was increased by 150 per cent.

So, we can see the need was recognized as early as 1939, and authorization for a moderate number of aircraft was given. One reason production was able to tool up so quickly, however is mentioned here:

Because the Air Corps had anticipated these authorizations, there was little delay in inaugurating its expansion program. As early as autumn of 1938 the Chief of the Air Corps had asked American aircraft manufacturers to prepare for an unprecedented growth, though no orders could then be guaranteed to them.9 By the time the new appropriations had been approved, contracts were being negotiated and tooling-up had begun.

So preparations were begun before the authorizations actually cleared congress. The direct results of the conflict over Britain can be seen later in the changes to the numbers of planes authorized:

To take advantage of approved increases in aircraft and personnel, the Air Corps in the spring of 1939 formulated a plan calling for 24 tactical groups to be combat-ready by 30 June 1941.10 Long before this objective was reached, however, the trend of events abroad urged further expansion, and in May 1940 the Air Corps projected the 41-group program.11 Within two months the goal was again revised upward in the 54-group program, which would provide an air force of 4,00 tactical planes, 187,000 enlisted men, 15,000 aviation cadets, and 16,800 officers.12 In autumn of 1941, the Army Air Forces, in anticipation of the vast expansion contemplated in the as yet unapproved Victory Program for munitions, formulated the 84-group program, which would enlarge the force to a personnel strength of 400,000 by 30 June 1942.13

You can see we started requesting the formation of 24 tactical groups, but in the summer of 1940 this changed, to 41 and then 54 desired air groups. You can see the direct effect the Battle of Britain was having.

Besides the why we needed these aircraft question, a point of interest is How did production ramp up so quickly

The aspect of expansion which was most eagerly followed by the American public was the rapid growth in the output of military aircraft. The seemingly miraculous accomplishments in this respect were essentially civilian rather than military. they were made possible through the fortunate combination of a highly adaptable industry, great national resources, and generous government aid; but the Air Corps played here a significant, if lesser, part. Contracts in 1939 were awarded on the basis of single-shift production, but factories moved steadily into a two-, then a three-shift schedule as more trained personnel became available.15 The Air Corps, along with the Office of Production Management, adopted carious methods of acquainting manufacturers with new types of aeronautical equipment, of spreading production among more firms, and of increasing the capacity of the industry. "Educational orders" were placed with manufacturers, existing facilities were enlarged by the aid of government financing, and new plants were built by the government for operation by private firms. "Letter contracts" saved from one to three months in initiating the fabrication of aircraft by permitting manufacturers to purchase materials before a formal contract could be drawn up and signed.

Competitive bidding was supplemented by the more rapid procedure of direct negotiation of contracts. In general, the Air Corps profited by its long and intimate association with the aircraft industry. Friendly personal relations made for mutual confidence, and reliance upon a telephone conversation or a quick airplane trip frequently obtained results which would have required weeks of formal correspondence. Some of the new methods were more expensive than the traditional ones, but by 1940 the nation, though it is now easily forgotten, had more money than time. In some ways the Air Corps was able to exert a direct influence on speeding up production. Standardization of aeronautical equipment was one method. This subject had been under study by the Army and Navy for more than a decade. Joint efforts toward standardization had begun with such minor items as nuts, bolts, and pressure pumps. By the time rearmament began the Army and Navy were procuring aircraft engines from two major contractors under terms which made most models equally acceptable to either service. Further efforts were made toward standardization of aircraft and related materiel used in common by the U.S. and British services. Such a policy was advantageous to both manufacturers and purchasers; it facilitated mass production, lessened confusion for the producer, and reduced overhead costs. Again, the Air Corps was able to reduce the long delays usually experienced in testing new models for acceptance. An accelerated service-test procedure was instituted whereby experienced crews in relays gave an airplane 150 hours of almost continuous flight with a full military load. This system brought to light i one month defects which formerly might have required a year of service testing for discovery.16

So these are some of the processes which allowed the increased rates in production. Some questions concerning which service branch these planes were targeted for is also addressed here:

These speed-up measures had begun with the initial appropriations for Air Corps expansion and had been intensified as U.S. and British demands increased. The 1939 Air Corps objective of 5,500 planes was soon raised to 10,000. Then on 16 May 1940, with the extension of the war in western Europe, the President called for an annual output of 50,000 aircraft and a total Army and Navy strength of the same number of planes; approved figures provided 36,500 for the Army, 13,500 for the Navy.


There are two elements to be considered in your question:

First, about the difference in mlitary spendings and aircraft production: what should be considered as completing the difference costs are all the weaponized aircraft exportations made by the USA to other countries: French Air Force, Thailand, Great Britain, the Netherlands... There are plenty of them. I asked a question about that.

Second, about the consideration of air forces in the USA. Because of its geographical position, the USA were forced to consider navy and air force as primary important elements. On the other hand, they were more likely to consider the Army as a tool that could be raised from scratch on a longer timeframe. Many specialized units, such as the Marines, played a crucial role in the beginning of the war while the bulk of the army came later in the fight.


This to try to clear up the questions raised by the a comment on the state of the U.S. Army Air force in 1939. The first issue is that there were two branches of the military, with an air force; the Army and the Navy. Although the Army was more important over the course of the war, the Navy was more important over the 1939-1942 period. By December 31, 1941, it had thousands of planes and pilots in action, a lot more than "55." These resources won critical battles at Coral Sea, Midway, and elsewhere in the first half of 1942. More to the point, it was the U.S. Navy (and naval aviation) and not the U.S. Army that represented America's main line of defense in 1941, behind a "two ocean" moat.

The other thing to remember is that 1939 is NOT 1941. It took about 18 months to train an American pilot. It is true that as late as 1940, America produced less than 4,000 planes, but there was a steep gradient to 1941. This Wikipedia source gives a somewhat different picture of the situation then than Kennedy. Even so, the basic premises of the question stand.

Wikipedia gives a (rounded) figure of 18,500 planes produced by the U.S. in 1941 (versus 26,000 by Kennedy). This compares to total production for that year of 19,000 by the three Axis nations, and 20,000 for Britain (Kennedy). That is to say that 1941 U.S. aircraft production was probably of the same order of magnitude as the other parties.

It is interesting to note that about half of the 18,500 U.S. produced planes in 1941 were "trainer" planes. The U.S. was not officially at war for most of that year, until Pearl Harbor, but war was clearly on the horizon, which is why "training" was so important. Put another way, the fliers of these "training" aircraft would be flying combat planes in 1942, 1943 at the latest, when U.S. production shifted over to this type of aircraft. That would be the case in the later years, even though a large proportion of combat aircraft went to e.g. Britain in 1941, because they had more trained pilots.

So (relative) U.S. air preparedness in 1941 was driven by the U.S. Navy, and due to the longer lead times required to train pilots than infantrymen, or even sailors.

  • It seems the confusion in production numbers stems from the 26,000 figure, being the cumulative total of the years 39-41. In the same time frame the UK produce ~42,000 planes. It appears the cumulative total is being compared to the single year number for 1941 UK. possibly contested wiki numbers
    – justCal
    Feb 24, 2020 at 13:39

Question: Why was America much better prepared earlier in World War II in the air than in other respects?

Yet by 1941, America produced 26,000 planes, more than either Britain or Russia (singly), as well as all the Axis nations combined. Put another way, the 1941 base was so high that U.S. aircraft production rose "only" threefold from 1941-1943, versus eightfold for total armaments spending.

Why the US was able to dramatically increase aircraft production in WW!!? Three primary factors.

  1. The United States entered the war on Dec 7th 1941 but they had been preparing for war for more than two years by that time. Aircraft production in WWII benefited from all that ramping up time, especially the ramping up of the aluminum production, as well as the building of new factories which are attributed to FDR's challenging U.S. business and industry before Dec of 1941.

Aluminum Production WWII
1939 – President Franklin Roosevelt asked Congress in 1939 for $300 million to build airplanes for the Army Air Corps, which had only 1,700 aircraft at the time. Congress agreed to pay for 3,251 aircraft.
1941 – The federal government admitted the severity of the aluminum shortage in the U.S. by February 1941 and called for expanding production to 423,000 tons per year, with very little allowance for civilian consumption. The National Defense Advisory Committee headed by Sen. Harry Truman played a role in promoting increased aluminum production for aircraft production during the war.

How Ford's Willow Run Assembly Plant Helped Win World War II
President Roosevelt stunned millions of listeners when he announced during a May 26, 1940, fireside chat that government must “harness the efficient machinery of America’s manufacturers” to produce 50,000 combat aircraft over the next 12 months to confront the “approaching storm” of global war. FDR’s goal exceeded the total of all planes built in the U.S. since the Wright brothers’ 1903 flight at Kitty Hawk, NC, and he challenged the aviation industry to match that number in succeeding years. As he spoke, the country had fewer than 3,000 warplanes in its arsenal, most obsolete.

  1. The United States industrial base was the largest in the world in 1940 and it had the wartime advantage of not being bombed regularly by the Germans compared to the UK's industrial base.

  2. The United States was able apply industrial techniques to large aircraft production. Conventional wisdom was that airplanes, especially the larger bombers were too complex to be Mass producted. As the US transformed it's civilian industrial base automobile manufactures like Henry Ford were put to work on mass producing airplanes. To deliver the kinds of numbers the country needed, aircraft production had to go beyond traditional aircraft industry and call upon experts in mass production who weren't involved previously with aircraft. This had dramatic effects on airplane production. Just, Ford's Willow Creek factory was able to produce as many planes as four conventional factories and at it's peak in 1944 produced 1 heavy bomber per hour 24 hours a day, 7 days a week; or nearly 9% of all US airplane production in 1944 from just that factory.

How Ford's Willow Run Assembly Plant Helped Win World War II
Automobiles of the era had 15,000 parts and weighed around 3,000 pounds. Sixty-seven feet long, the B-24 had 450,000 parts and 360,000 rivets in 550 sizes, and it weighed 18 tons. Skeptics dismissed mass production of a plane this enormous and advanced as a carmaker’s fantasy that would crash and burn when repeated design changes disrupted assembly lines and junked expensive tooling. “You can’t expect a blacksmith to make a watch overnight,” sniffed Dutch Kindelberger, president of North American Aviation.

Ford proved them wrong, not easily nor entirely, during a 2.5-year production run in a 3.5-million-square-foot factory built over Willow Run Creek near Ypsilanti, MI. The massive plant turned out 8,645 Liberators vs. 9,808 manufactured by four factories of Consolidated, Douglas Aircraft, and North American Aviation. Together they produced more of the slab-sided behemoths than any American warplane ever.

At the request of the government, Ford began to decentralize operations and many parts were assembled at other Ford plants as well as by the company's sub-contractors, with the Willow Run plant concentrating on final aircraft assembly. The bugs were eventually worked out of the manufacturing processes, and by 1944, Ford was rolling a Liberator off the Willow Run production line every 63 minutes, 24 hours a day, 7 days a week.

So in 1944 the US produced 96,270 aircraft, about 9% or 8343 planes came from just one Ford Willow Creek factory.

8343 calculated from 1 plane every 63 minutes 24 hours a day, 7 days a week in 1944.

The US employed both manufacturing techniques during WWII for aircraft, not just massed production.

I think your numbers are wrong. The US produced only 18,466 aircraft in 1941 while Great Britain produced 20,094. see WWII Aircraft Production it wasn't until 1942 that the United States out produced the UK in aircraft production.

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