Why did the USA sell so many airplanes prior to WW2?

Question:
I am wondering why there are so much airplanes made in USA in the world's air forces prior to WW2, since I don't think the US Air Force had the better reputation. You can count the:

• Glenn Martin fighter
• Brewster F2A Buffalo fighter
• Martin Twin engine bombers in multiple variants

Short Answer:

It wasn't really about the quality of the product or the cost. It was about countries desperate for modern warplanes as either war was on the horizon or already upon their doors. The countries with superior offerings, like Britain were desperate to add more planes to account for their limited domestic production. Other countries like Finland and Belgium were even more motivated to take any modern equipment available.

When WWII began prior to the United States entering, all "modern" monoplane fighters were in high demand. The United States was a country with some limited airplane production during this interwar period and was willing to allocated significant parts of that modest production to countries desperate to catch up to Germany in re-armament.

Detailed Answer

The United States did not maintain interwar aircraft production capacity to maintain it's own modest needs much less act as a significant exporter of aircraft. As late as 1938 the US Army Air Corps had 10% fewer planes than authorized by Congress. In 1939 the United States only produced 921 warplanes, including bombers, torpedo planes and fighters. In 1940 1,771. The interwar production capabilities of the United States were a far cry from WWII peek of 1944 when the United States was producing 74,564 combat aircraft per year.

1938
-Aviation in the US. Army, 1919- 1939
The Air Corps then owned 2,100 serviceable planes, 220 below the number authorized by Congress. President Roosevelt believed the Air Corps needed 20,000 but did not think Congress would approve so many. He called for production of 10,000 aircraft for the Army over 2 years. Generals Arnold, Craig, and Marshall were among those who heard the President outline his program at the White House on November 14, 1938. Afterwards, they tried to balance airplane production with provisions for pilots, maintenance, supplies, and facilities. The War Department also sought to balance the Army as a whole. The Navy asked for more money. This was not what the President had in mind, but he adjusted his program and on January 12, 1939, asked Congress for $300 million to produce at least 3,000 aircraft. Congress responded by raising the Army’s airplane authorization from 2,320 to 5,500, approving procurement of 3,251 planes, appropriating money to start the program, and raising the officer authorization to 3,203 and the enlisted to 45,OJOO.

So while the US had production it had nowhere near the production we think of when we think of WWII. In the Interwar period the United States didn't even purchase enough modern war planes for it's own use to justify competitive production cycles with the great powers of Europe.

As for the planes you mentioned.

Brewster Buffalo was introduced April 1939. It was sold to Britain, Netherlands and Finland once WWII began. Even though it was a new plane and the United States was desperately trying to modernize it's own air service, the United States sold the Buffalo as surplus in a pre lend lease policy of exporting arms to Europe. Although it was inferior to both Britain and German contemporary aircraft it was still deemed useful for countries desperate for any military aircraft once WWI began.

Brewster Buffalo

American Reporter —Ralph Ingersoll wrote: In late 1940 after visiting Britain that "The best American fighter planes already delivered to the British are used by them either as advanced trainers --or for fighting equally obsolete Italian planes in the Middle East. That is all they are good for" —in the early years of World War II all modern monoplane fighter types were in high demand. Consequently, the United Kingdom, Belgium, and the Netherlands East Indies purchased several hundred export models of the Buffalo

Martin B-10
Is probable the best example for your question. While it was introduced in 1934 and was a significant achievement for the US airplane producers at that time it was obsolete by the time WWII came around. It was built as a private venture by the company, it's sales correspond to it's performance and inexpensive price. As one of the first mass produced bombers.

The export version was the Model 139W. Argentina received 25, China (9) nine, Siam (6) six, Turkey (20) twenty, Russia (1) one, and the Netherlands 117. Only the first 39 Netherland aircraft were 139Ws which was similar to the B-10B. The remainder were designated as the Model 166 which had a long greenhouse canopy connecting both the forward and rear c**kpits.3

The total production of all B-10 versions was 348 aircraft with 166 for the USAAC and 182 for export. Operators included Argentina, China, Netherlands, Philippines, Thailand and Turkey.

Martin fighter
I could find no record of Martin ever making a fighter plane in either WWI or WWII. It was famous for it's bombers in WWII and trainers in WWI.

Sources:

• Brewster F2A Buffalo
• United States Aircraft Production During WWII
• 300,000 Airplanes
• Aviation in the US. Army, 1919- 1939
• Martin B-10