Enhanced security checks on electronic devices mean passengers on US-bound flights will have to leave them behind if the batteries are flat.
US homeland security secretary confirmed that enhanced security checks would be implemented immediately at some airports abroad as experts believe terrorists have devised how to turn phones into explosive devices that can avoid detection.
And it said 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.
The US Transportation Security Administration has warned: "Powerless devices will not be permitted onboard the aircraft. The traveller may also undergo additional screening."
Britain’s Department for Transport (DfT) advised that the new restriction meant any electronic device with a flat battery would not be allowed on flights, the Press Association reported.
The head of the Parliamentary committee that overseas the work of Britain’s intelligence agencies says airport security measures are "sadly unavoidable".
Conservative MP Sir Malcolm Rifkind says there is more to the threats than has been made public and warns against complacency.
Writing in The Sunday Telegraph, Sir Malcolm said: "It is simply foolish to believe that the threat is either minimal or now behind us.
"We have, indeed, been fortunate but, sadly, this has not been because the terrorists have, since 2005, given up trying to do us harm.
"Each year there have been serious plots which if they had not been identified and disrupted would have led to the deaths and mutilation of many British citizens."
He added: "I have received fuller information than it has been possible to publish in the newspapers. I have no doubt, from what I have learnt, that these new steps are not bureaucratic nor an overreaction. Sadly, they are unavoidable."
