US airport security checks target electronics
7 July 2014 Last updated at 07:24 BST
A number of airports, including Heathrow, have been ordered to intensify screening of electronic devices.
American transport officials said in a statement that passengers could be asked to switch on devices, and equipment that does not power up would not be allowed on board.
The US announced new security measures last week, apparently in response to a terror threat, but gave no details.
Tom Esslemont reports from Washington.