Goodbye, Farewell, and Amen - S11-E16
Visible crew/equipment: While Klinger is on the phone trying to set up BJ's transportation home, just as Winchester walks into the office pointing out the company clerk the shadow of the moving boom can be seen on the wall, and it's also visible when Winchester takes the mailbag and dumps the contents. (00:42:50)
Answer: The C-42 was a military variant of the Douglas DC-2. Very few C-42's were built, so it's questionable that Potter would specifically have seen that particular model, but, given his military background, it's not entirely unreasonable that he might use the military designation even when the aircraft in question is actually a civilian DC-2.
Tailkinker ★