Three thoughts immediately come to mind: 1. I'm sure there is some aviation related regulation that prohibits it. 2. I'm sure the airlines wouldn't

Three thoughts immediately come to mind: 1. I'm sure there is some aviation related regulation that prohibits it. 2. I'm sure the airlines wouldn't be happy about the competition posed by your friend. They must be making a tidy profit on offering WiFi on flights. 3. A plane being mostly aluminum is probably like a Faraday cage and satellite signals might not get in or out well.