WHat kind of diaper change was that?
I would probably draw the line between two ahem common scenarios. And a couple times i had to change diaper in the seat (the less offensive kind ) because seatbelt sign was on in one case and there was a loooong line in another and current diaper leaked.

The choice was to essentially slowly soak myself, kids clothes and eventually the seat while waiting or make a quick change - i opted for the latter. Would definitely prefer doing it in a lav given an option.