The Douglas Aircraft Company was an early American aerospace and defense firm that was based in Southern California. The company was founded in 1921 by Donald Wills Douglas Sr. In its early days, one of its aircraft was the first to circumnavigate the world by air, and the company became well-established during World War II thanks to designs such as the C-47 Skytrain, the A-26 Invader. It also collaborated with Boeing on the B-17 Flying Fortress, but suffered several cutbacks after the end of the war.