McDonnell Douglas was a major American aerospace manufacturing corporation and defense contractor formed by the merger of McDonnell Aircraft and the Douglas Aircraft Company in 1967. Between then and its own merger with Boeing in 1997, it produced a number of well-known commercial and military aircraft such as the DC-10 airliner, the F-15 Eagle air superiority fighter, MD-80 airliner and F/A-18 Hornet multirole fighter.

The corporation was headquartered at St. Louis Lambert International Airport near St. Louis, Missouri, and its subsidiary, McDonnell Douglas Technical Services Company (MDTSC) was based at another location in St. Louis County, Missouri. At its peak in mid-1990, McDonnell Douglas employed 132,500 people. By the end of 1992, employment had dropped to approximately 87,400.

Hughes Helicopters was a major manufacturer of military and civil helicopters from the 1950s to the 1980s.

The company began in 1947, as a unit of Hughes Aircraft, then was part of the Hughes Tool Company after 1955. It became the Hughes Helicopter Division, Summa Corporation in 1972, and was reformed as Hughes Helicopters, Inc. in 1981. However, throughout its history, the company was informally known as "Hughes Helicopters". It was sold to McDonnell Douglas in 1984 and made a subsidiary under the name McDonnell Douglas Helicopter Systems. See MD Helicopters for history of the company after this acquisition. In 1997 McDonnell Douglas merged with Boeing with Boeing as the surviving company.