It sounds like I"ll give my Magellan RoadMate a try. I wonder if the airspeed is too fast for it to be able to acquire a satellite? It always takes a few minutes if I turn it on after I've started driving. If 35 mph slows it down, I can only imagine what 500 mph does!!

The advantage of a GPS to me would be the ability to track the route while watching another channel or listening to music.