That is a previously reported -- many times -- bug that has not yet been resolved. That is that an automoving plane of the slow type (N17 Fokker, etc.) suddenly moves three spaces, when its fastest possible legal move is two spaces.

Happened to me over New Year's as well.

I suspect what is happening is that the automove logic is allowing autmoved planes to select from a larger "pallette" of moves than it should ...