At the beginning of Operation Barbarossa, the Red Air Force was devastated on the ground and the Germans quickly established air superiority. How did the soviets recover from this? Did they face a shortage of experienced pilots like a Japan and Germany eventually did?
Industry and experience.
The Soviets had around 10k+ planes, while Germany had at most 5k at the start of Barbarossa.
Hermann Göring was told by the experts, from Daimler-Benz, Henschel and Mauser that one aero engine factory in the Moscow region was six times larger than six of Germany's largest factories put together. Göring was furious with the report, and dismissed it. He believed they had fallen for a Soviet bluff.
Germany didn't have enough intelligence in the SU to see how massive the industry in the Urals was that was supporting the Soviet Air Force. The factories in the Urals were mostly safe from bombing while German factories got bombed relentlessly from both fronts. As a result, German fighter and bomber production reduced in both number and quality, while the Soviets had their factories producing planes unhindered.
On October 15, 1940; General Tschersich, the Luftwaffe's chief of procurement, was basing aircraft replacement on the assumption peace with Britain would be secured, and there would be no further military operations until 1 April 1947.
In short, the Germans thought the Soviets didn't have planes and even if they did, were inexperienced. The Luftwaffe was also under the assumption that there was not going to be a war on the East and thus didn't ramp up production. They just produced planes equal to the amount they lose in the fight over Britain.