like its dc-9/md-80/md-90 predecessors, the 717 has a 2+3 seating arrangement in the main economy class, providing only one middle seat per row, whereas other single-aisle twin jets, such as the boeing 737 family and the airbus a320 family, often have 3+3 arrangement with two middle seats per row. unlike its predecessors, mcdonnell douglas decided not to offer the md-95/717 with the boarding flexibility of aft airstairs, with the goal of maximizing fuel efficiency through the reduction and simplification of as much auxiliary equipment as possible.