Continuity mistake: When Mulcahy is describing a person who was "quite a Bozo" to Potter, Potter realizes who he is referring to. Mulcahy's arm is close to the table. When the camera cuts to Mulcahy's face, his mug is close to his face.
Continuity mistake: When Potter is chewing out Klinger about the morning reports, the camera is looking at Potter. As he finishes his line with "once in a while", he puts his right arm down. When the camera cuts to look at Klinger from behind Potter, his (Potter's) arm is up and finger pointing at Klinger.
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 ★