He founded the Douglas Aircraft Company in 1921 (the company later merged with McDonnell Aircraft to form McDonnell Douglas Corporation). Under his leadership, the company became one of the leaders of the commercial aircraft industry, engaging in a decades-long struggle for supremacy with arch-rival William Boeing and his eponymous enterprise. Douglas gained the upper hand, particularly with his revolutionary and highly successful Douglas DC-3 airliner and its equally popular World War II military transport version, the C-47; at the start of the war, his airplanes made up 80% of all commercial aircraft in service. However, he lagged behind in the jet age and was overtaken and surpassed by Boeing. He retired in 1957.