Originally Posted by
controller1
Yet a child under the age of 2 may be held in the lap and potentially become a human projectile.
That's why you also can't put your child in the seat pocket, but you can just hold on to your laptop.
Or more seriously, whether you can start using your phone after the aircraft left the active runway following touchdown, or until it's at gate. Or, whether it's under 10,000ft when you need to turn off electronics, or it's "whenever" the crew feels like telling the passengers.