I believe a number of the NW DC9's made it past 40 years old when retired by DL. Here's a cranky flier article that mentions a 1968 build DC9-40 that made it to 2011. I suspect none of the current aircraft in the fleet are going to last that long.
https://crankyflier.com/2011/01/18/d...hwest-compass/
Last edited by xliioper; Sep 29, 2019 at 10:47 pm