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 St. Louis's Lambert International Airport, in Berkeley, Missouri, near the city of St. Louis. The McDonnell Douglas Technical Services Company (MDTSC), a subsidiary of McDonnell Douglas, was headquartered in unincorporated St. Louis County, Missouri, United States. McDonnell Douglas later merged with its rival Boeing in 1997.