I seem to recall, for football, at least, a trip needs to be more than 500 miles to allow a flight instead of a bus trip. The distance from Grand Forks to Houghton is 477 miles.
A few years ago when the football team played at Michigan Tech in the playoffs, they asked the NCAA if they could fly instead because it was a playoff game, and they were allowed to do so.
I'm not sure if the same rules apply to hockey, though.