The Boeing 717 is an unusual aircraft with a complicated history. It was originally developed by McDonnell Douglas as the MD-95, a modernized successor to the DC-9 and MD-80 families. When Boeing acquired McDonnell Douglas in 1997, the program was rebranded as the Boeing 717 and put into production. The aircraft entered service with AirTran Airways in 1999 and found its niche on short-haul, medium-density routes where a 737-700 would have been too large and a regional jet too small. Boeing ended production in 2006 after only 156 aircraft had been built. Delta Air Lines inherited a large 717 fleet from AirTran through the Southwest merger in 2011 and has operated it since, though retirement is planned in the late 2020s. The 717 is known for its rear-mounted engines, quiet cabin, and distinctive single-aisle 2-3 seating layout.