Uncharged mobile phones, tablets and laptops will not be allowed on US-bound flights after a warning al Qaeda could be planning to blow up an airliner.
The US Transportation Security Administration (TSA) said passengers at certain international airports may be asked during security screening to turn on their electronic devices.
If they do not have power the devices will not be allowed on planes, said the agency.
The TSA would not specify which airports would be subject to the extra screening.
However, Britain's Department for Transport warned UK passengers: "If your device doesn’t switch on, you won’t be allowed to bring it onto the aircraft."
US security officials said last week they fear bombmakers from the Yemen-based al Qaeda in the Arabian Peninsula (AQAP) have worked out how to turn phones into explosive devices which can avoid detection.