I am pretty sure internet in the sky, with any speed and throughput is either going to come from Air Cell.... with dedicated transmitters and antennas pointed up.... or from satellites. The ground cell network just doesn't cut it.
Back when analog was common, I used the phone reliably all over the west at up to 15K ft. Digital is another story. Even the very very high end sat systems don't have the bandwidth we are used to on cable. One of my customers expected NFL and freeze frame/instant playback on his G-5 with a high dollar, steerable antenna system. He was disappointed.
Iridium works well for low cost emails and texting. Not very fast though.
Flightcell makes a nice aircraft receiver that does terrestrial cell and satellite. It switches to which ever is cheaper and works... all hands off.
"Kindness is never a bad plan."
Work bio: Avionics tech support; ATP rated in planes.Helicopter rated, balloon instructor, seaplanes and for grins, Phantom Drone pilot. Instructor for air medical and law enforcement tactical radio systems. Fly my RV9A to work every week. Janitor when and as needed.