I worked for Jetway/Mark Air Transport out of YIP from 1978 to 1980. I was in KCK (Kansas City Fairfax) one day when 421AJ came in over the dyke between the Missouri River and the runway. That was one scary piece of flying. I was told that 421AJ couldn't be painted because the mechanics needed to be able to check on the amount of corrosion a DC 8 could have and still be airworthy! Tongue in cheek, I'm sure but that was one ratty looking freighter.