[I searched for an answer, but could not find one. Forgive me if it's out there and I missed it]

When is the satellite-based internet active on the 77W? Is it something you can activate while on the ground during boarding, and have the purchased access be valid for the entire flight? Or, does it only become active when above 10,000 feet or at some other point during the flight? I know that laptops and other larger devices can't be used while taxiing and when below 10,000 feet, but that's not my question. Smaller internet-enabled devices can now be used during all phases of flight, and laptops can be used during boarding.

The obvious related question is when does it stop working? Upon landing? Earlier? Or is it active until after you actually get off the airplane?