You know how airport security will occasionally ask you to turn on a phone or laptop to prove that it isnt hiding explosives? Well, thats no longer just a rare inconvenience — if you take certain flights, its mandatory. The TSA now requires that you power on your gadgets when flying to the US from certain overseas airports. If you have a dead battery, youre out of luck. Youll likely have to leave that hardware behind, and you might go through additional screening at the same time.