Air passengers flying to the United States will have to make sure their mobile phones and tablets are charged.
Officials may ask travellers to turn on their electronic equipment to show they have power.
The US Transportation Security Administration (TSA) said in a post on its website: "During the security examination, officers may also ask that owners power up some devices, including cell phones.
"Powerless devices will not be permitted onboard the aircraft. The traveller may also undergo additional screening."
The changes are part of increased precautions due to the threat of terrorist attacks.