Other mistake: Radar says the weekly report is for the 17th to the 22nd inclusive. A 6 day week in the middle of a war?
Other mistake: The Chinese patient cut the strap of Klinger's red gown, but Radar says Klinger requests a replacement brassier. Later Klinger's red gown shows no damage, although he could have retied the strap.
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 ★