Northwest Airlines was a major United States airline which existed from 1926 until 2010, when it merged with Delta Air Lines. At the time of the merger it had a total of 309 aircraft. It was also the last U.S. airline to have a dedicated cargo fleet and routes. Northwest, unlike Delta, operated a mixed fleet of Boeing, McDonnell Douglas, and Airbus aircraft. The Boeing 757 was the only type of jet common to the pre-merger fleets of both Delta and Northwest. The Northwest fleet was integrated into Delta's fleet on December 31, 2009. The airline ceased operations and merged into Delta in 2010. Most of Northwest's Boeing 747 fleet was sent to Delta which had retired all of its own 747s in the 1970s. (en)