I've used GPS on planes many time, whether it be phone or handheld Garmin. I do tend to be a little discreet about it, in these times.
@ Dominican, you are wrong about the line of sight part. Civilian GPS uses the 1.5 Ghz band. That frequency range is attenuated by quite ordinary materials, e.g human body, tree cover etc, and certainly wont penetrate any 'structures'. Particularly the faraday cage of a jet.
The signal will reflect from some materials. But that is likely to cause errors rather than help, as bounced signal will have a longer delay and thus decrease accuracy.
However if you hold the device near to the window, you may be lucky enough to get the minimum 3 satellites for a signal (4 for 3D nav).