The McDonnell Douglas DC-9 is a twin-engined short-to-medium-range narrowbody airliner with a capacity of maximum 139 passengers produced by the American manufacturer McDonnell Douglas (originally Douglas Aircraft).

The original DC-9 was produced in the following main series: DC-9-10, DC-9-20, DC-9-30, DC-9-40 and DC-9-50.
The first variant DC-9-10 has a total length of 31,82m (104ft 5in) and a wing span of 27,25m (89ft / 5in) with accommodation up to 109 passengers. (total 137 aircraft)
The DC-9-20 was produced in the variant DC-9-21 only (total 10 aircraft), it was the fourth model of the DC-9. This model was a combination of the fuselage of the DC-9-10 and the wings of the DC-9-30.
The DC-9-30 was a development with a stretched fuselage (36,36m / 119ft 4in) and a increased wing span (28,44m / 93ft 4in) with accommodation up to 127 passengers. (total 662 aircraft)
The DC-9-40 was a further lengthened variant (38,28m / 125ft 7in), accommodation up to 128 passengers. (total 71 aircraft)
The DC-9-50 is the largest variant with a total length of 40,72m (133ft 7in) with accommodation up to 139 passengers. (total 96 aircraft)
Further developments are the McDonnell Douglas MD-80 & MD-90 and Boeing 717.
Engine Options:
DC-9-10: Pratt and Whitney JT8D-1/-1A/-1B/-5/-7/-7A/-7B/-9/-9A/-11/-15/-17
DC-9-20: Pratt and Whitney JT8D-9/-9A/-11
DC-9-30: Pratt and Whitney JT8D-1/-1A/-1B/-5/-7/-7A/-7B/-9/-9A/-11/-15/-15A/-17/-17A
DC-9-40: Pratt and Whitney JT8D-9/-9A/-11/-15/-15A/-17/-17A
DC-9-50: Pratt and Whitney JT8D-15/-15A/-17/-17A