Not to mention NW DC-9s (including after the merger with Delta). They were last produced in 1982 and a family member flew on one in 2013 on Delta.

ETA: I had a 2007 flight from DTW on a DC-9 that was the source of one of the best cockpit PAs I've heard. The plane was mostly boarded when the captain came on and announced that "someone noticed a puddle of oil under the right engine" and that "we're going to check that out for you." Turned out something was loose. It got fixed in pretty short order and we were on our way to PIT (with a full beverage service).