Travelers on US-bound international flights will have to prove to the TSA that their cell phone has power before boarding the aircraft in the name of security. From The Guardian:
Passengers using airports that offer direct flights to the US may be forced to switch on their mobile phones and other electronic devices to prove to security officials that they do not contain explosives, it was announced on Sunday.
“During the security examination, officers may also ask that owners power up some devices, including cell phones,” the US Transportation Security Administration (TSA) said in a post on its website. It warned: “Powerless devices will not be permitted onboard the aircraft. The traveller may also undergo additional screening.”
Better power up your phone before leaving for the airport.