McDonnell Douglas was a major American aerospace manufacturer and defense contractor, producing a number of famous commercial and military aircraft. It formed from a merger of McDonnell Aircraft and Douglas Aircraft in 1967. McDonnell Douglas was based at Lambert-St. Louis International Airport near St. Louis, Missouri.
The McDonnell Douglas Technical Services Company (MDTSC), a subsidiary of McDonnell Douglas, was headquartered in unincorporated St. Louis County, Missouri, United States. McDonnell Douglas merged with its rival, Boeing, in 1997.