That said, just because there is no passenger connectivity doesn't mean the airline doesn't have some, for operational reasons. Even if that's just a narrowband satellite or VHF (ACARS) link, credit card transactions take very little data (POS terminals are 80s technology, after all).

That said, I still don't think that that's too common – building out cabin Wi-Fi for card authorizations only is probably not worth it, given how hard it is to get away with fraud in an environment where every seat has a passenger name to it, and that name is often verified by the airline or government at the airport or at boarding time.