DC-9 / Northwest AirlinesNorthwest Airlines DC 9 airplane model. The DC 9 MD 80 MD 90 717 series, with its roots in the 70 seat DC 9 10 of the early sixties, has undergone extensive development unlike any other airliner in history. This short range complement to the larger DC 8 was first introduced on April 8, 1963, following an order from Delta. It featured a new design with rear fuselage mounted engines, a T tail, and moderately swept wings, providing seats for up to 90