The McDonnell Aircraft Corporation was an American aerospace manufacturer based in St. Louis, Missouri.

[3] He left in 1938 to try again with his own firm, McDonnell Aircraft Corporation, based at St. Louis, Missouri in 1939.

It grew from 15 employees in 1939 to 5,000 at the end of the war and became a significant aircraft parts producer, and developed the XP-67 Bat fighter prototype.

The advent of the Korean War helped push McDonnell into a major military fighter supply role.

In 1943, McDonnell began developing jets when they were invited to bid in a US Navy contest and eventually built the successful FH-1 Phantom in the postwar era.

The Phantom introduced McDonnell's telltale design with engines placed forward under the fuselage and exiting just behind the wing, a layout that was used successfully on the F2H Banshee, F3H Demon, and the F-101 Voodoo.

McDonnell made a number of missiles, including the pioneering Gargoyle and unusual ADM-20 Quail, as well as experimenting with hypersonic flight, research that enabled them to gain a substantial share of the NASA projects Mercury and Gemini.