I used my Garmin 96 on a Ryanair from PIK-STN last week and it worked fine, didn't need to "press it against the window" to get a proper signal but picked up more satellites if it was close to the window,
Pretty much good fun and a good way to wile away the trip. My readout was 455kts and pilot said we'd be flying at 37000ft and readout was 37263ft, due to flying flight levels and pressure varience. All good fun, I'd recommend it.