Why did the aviation industry decline after wwi, and what to revive it?

It declined because planes did not need to be created after the war for the planes were only used for war then for the most part. Companies ran out of business because planes were not being bought or at least not a lot or enough so they sold for dirt cheap. Then pilots who loved flying from the war bought them and they became barnstormers. People who travel across the United States or other countries performing stunts in towns everywhere.