Satellite is always what you get on planes if you fly over an ocean. If you're flying over land, sometimes it's satellite and sometimes it comes from ground-based cells. Depends on the airline and the plane's equipment.

Yes, it is. One of the biggest providers is called GoGo who in turn use satellites from SES. My comment about satellite was that I've also worked in very remote places using much poorer links and HN still works, amazingly.