Douglas DC-9-20

The Douglas DC-9-20 was a specialized variant developed specifically for operations from high-altitude airports and hot climates. Retaining the compact 31.82-meter fuselage of the DC-9-10, it featured more powerful Pratt & Whitney JT8D-11 engines producing 66.7 kN (15,000 lbf) thrust each and improved wing design for better performance in challenging conditions. The DC-9-20 was optimized for airlines serving airports like Denver, Mexico City, and La Paz, where thin air reduced engine performance and increased takeoff distances. SAS (Scandinavian Airlines) launched the variant in 1968, valuing its ability to maintain schedules from mountainous Scandinavian airports during summer heat. The DC-9-20 seated 80-90 passengers and offered a range of 2,963 km (1,605 NM). However, only 10 examples were built due to limited demand—most airlines preferred the larger DC-9-30. The DC-9-20 proved the design's adaptability but remained a niche variant. SAS operated theirs until the late 1980s.