US Army Air Corp Fighters on Hand During WW2

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Figure 1: Thunderbolt P47 with the French Air Force (Wikipedia).

Many years ago, at the start of my career, I worked with an excellent safety engineer who had served in WW2 as a fighter pilot in Europe with the US Army Air Corps (USAAC). You could tell that flying was the love of his life. Though we were working on naval weapons systems, our lunchtime talks often focused on his experiences flying aircraft during the war. His war service began in a P-47 (Figure 1) and his unit later transitioned to the P‑51 (Figure 2).

Figure 2: P-51 Mustang.

Figure 2: P-51 Mustang (Wikipedia).

Most of his flying was over Europe doing bomber escort. While he generally had good things to say about both aircraft, most of his stories were about the P-51. One day I asked him if he had a preference between the P‑47 and P‑51. He answered with no delay and I found his response so interesting that I wrote it down in my collection of quotes.

I wanted to be flying a P‑47 if someone was going to be shooting at me because there was no coolant to leak from its radial engine if I was hit. If I was just going flying, then I wanted to be flying a  P‑51. The P‑47 could dive very fast, but it did not climb well.

I started to wonder about units transitioning from one aircraft to another during the war. I decided to look at the Army Air Forces Statistical Digest (Hyperwar Site) to see if there was any information about fighter inventories during WW2. It turns out this document has several tables of aircraft inventory throughout the war. I used Power Query to Extract, Transform, and Load (ETL) the data into a quick report.

For those who like to follow along, my Excel Workbook can be downloaded here.


Excluding some obsolete fighters, the P-39 and P-40 were the main USAAC fighters on December 7, 1941. While both of these fighters had their strengths, they both had weaknesses relative to fighters like the Luftwaffes's BF-109 and Imperial Japanese Navy's A6M Zero.  As quickly as possible, the P-39 and P-40 were replaced with the P-38, P47, and P-51. My workbook will look at this transition and how quickly it occurred.


My analysis method is straightforward:

  • Use Power Query to directly download the download the data from the Hyperwar web site.
  • Because the data is in multiple tables, develop a function that could process each table the same way.
  • Apply the cleaning function to each table and consolidate the data.
  • Plot the data.

Figure 3 shows the USAAC's on-hand first-line fighters during WW2. We can make some observations about how the on-hand fighter inventory varied:

  • The P-47 numbers ramped up starting in mid-1942 and pretty much flattened out by mid-1944.
  • The P-51 numbers started to ramp up in the second quarter of 1942 and continued to ramp until just before Victory of Japan Day (VJ-Day).
  • P-39 and P-40 numbers began to decrease in early-1944. The P-39 did provide good service with the Soviets and the P-40 did well on ground support in the Mediterranean and North Africa.
Figure 1: USAAC Fighter Inventory During WW2.

Figure 3: USAAC Fighter Inventory During WW2.


The on-hand inventory data shows that the P-47 was the most numerous USAAC fighter through most of WW2. Its numbers stayed roughly constant after April-1944. The P-51 inventory ramp-up started later and was more gradual than that of the P-47, but they ended the war with similar on-hand numbers.

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3 Responses to US Army Air Corp Fighters on Hand During WW2

  1. Patrick L Boyle says:

    The point I'd like to make about the P-38 is that it was in many ways the most interesting and effective fighter of the war but alas was too expensive.

    It is commonly said that we never could have fighters accompany our heavy bombers all the way to Berlin until we got the P-51. That's not true. The P-38 actually had a little more range. In a strange twist of history the Nazi sympathizing Lindberg showed American pilots in the Pacific techniques for extending the range of the P-38. Using those techniques our pilots conducted the famous long range raid that shot down and killed Yamamoto.

    The P-38 was an exceptional one-on-one combat plane. It wouldn't be proper to call it a dog fighter because it generally used different tactics - more swoop and flee. Get altitude and come in fast. I believe the P-38 had the best climb rate of any fighter in the war. Somebody check on that for me.

    Out best (Bong) and second best scoring pilots flew P-38s. Because it mounted its machine guns and cannon in the nose between the two contra rotating engines it was a very stable gun platform. The guns fired straight unlike almost all the other fighters which had wing guns that converged.

    So why did they make all those P-51s and not P-38s?

    The P-38 cost almost exactly twice that of a P-51. Makes sense. A P-38 is sort of two planes stuck together. But it was even worse. The P-38 was not supercharged like almost all other fighters it was turbocharged. Turbocharging was better but required a bigger plane than most fighters could manage. Turbos then had great long pipes everywhere. The huge bulbous P-47 was big enough and so were the bombers but not the little Spitfire, Bf-109, or P-51.

    The turbochargers required scarce strategic materials like tungsten. Depriving the Nazi's of tungsten was as major victory for our side. The Nazi's had almost no tungsten carbide tank shells. They had to reserve what little they could get for machine tools. We had a more, but reserved the turbochargers for the most part for bombers not fighters.

    The P-38 was in fact a good dog fighter but only if the pilot had special training. Master pilots could turn on its axis more quickly by controlling the power to the engines - to turn right tighter you could feather the right engine. Not all pilots had this training.

    So the P-38 cost twice as much as a P-51 (two engines instead of just one) and needed twice as much training for the pilot and used strategic materials. Add to that all the many development problems because of its great complexity and its cold cockpit and the choice went to the much less interesting P-51.

    • mathscinotes says:

      The success of most systems depends on where they are deployed and the level of training people have. I also am sure cost was a big deal. I have read about the success of the P-38 in the Pacific war. In Europe, I have read there were problems early on that were only alleviated with later models (link).

      It sounds like a great plane in the hands of an experienced pilot, but could be trouble for a newbie. I recall watching a video of Robin Olds, who was an ace in both the P-38 (5 kills) and the P-51 (8 kills). Here is a comment he made about the P-38.

      “I loved the P-38 but I got those kills in spite of the airplane, not because of it,” Olds recalled. “The fact is, the P-38 Lightning was too much airplane for a new kid and a full-time job for even a mature and experienced fighter pilot. Our enemies had difficulty defeating the P-38 but, as much as we gloried in it, we were defeating ourselves with this airplane.”

      Similar comments were made by Colonel Harold J. Rau.

      After flying the P-38 for a little over one hundred hours on combat missions it is my belief that the airplane, as it stands now, is too complicated for the ‘average’ pilot'. I want to put strong emphasis on the word ‘average,’ taking full consideration just how little combat training our pilots have before going on operational status.

  2. Jason says:

    The P-38 was a good dog fighter, but only if the pilot had a special training session. It cost twice as much as the P-51 (two engines instead of one) and required twice as much preparation for the pilot. The deprivation of Nazi tungsten was a huge win for our side. The P-47 was big enough, so were the bombers, but not the little Spitfire, Bf-109, or P-50. The option went to P-51, which was much less exciting and more complicated. The Battle of the Bulge will be televised by ITV1 at 9 p.m. tonight.

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