All electronic devices can emit RF...GPSr, CD players, laptop computers, etc. It's just up to the individual airlines as to whether they will allow you to use such devices. Some will some won't. However have you ever heard of a aircraft crashing because someone turned on a pager, or a CD player, or a DVD player, or a GPSr? Myth Busters (TV show) had one episode where they TRIED to interfer with the navigation system of an aircraft and couldn't. I think airlines are just being over cautious and in this day and age, maybe that's not such a bad thing.