Have you ever done this?
My trip to Las Vegas last week is the first time I've flown since I've had my GPS and I was eager to see how it would work from the confines of the sardine tube in the sky.
The answer is GREAT. Other than taking a bit longer to lock onto the satelites it easily tracked the speed, altitude and location of the aircraft.
I was even able to attach the GPS to the window of the plane so I could have it in front of me for the entire flight.
It was neat to follow the map and be able to identify the cities, towns and even bodies of water we were passing over. If you noticed the power cord coming from the unit, that's because I attached it to my laptop to power it for the duration.
The only downside is the restrictions on using electronic devices below 10,000 feet. (It would have been cool to see the GPS track us right down to the runway!)