Insider Threats
"the necessary Ethernet port for gaining access is in the 747's galley: an area rarely left unattended for more than a few minutes during flight. Using the exploits PTP found to pwn an in-flight 747 would be impossible in practice."
Unless, of course, the hacker is one of the flight attendants. Or the hacker connects an unobtrusive RJ45-to-wireless connector to the galley RJ45 port when boarding and then hacks from the comfort of their seat.