The McDonnell Douglas MD-80 is a series of single-aisle airliners developed by McDonnell Douglas from the earlier DC-9.Stretched, heavier, and with higher bypass Pratt & Whitney JT8D-200 engines, the DC-9 Series 80 was launched in October 1977.It made its first flight on October 18, 1979 and was certified on August 25, 1980. It was first delivered to launch customer Swissair on September 13, 1980, which introduced it into commercial service on October 10, 1980.