Airlines with direct flights to the US have been told to tighten their screening of mobile phones.
The warning comes as security experts believe terrorists have devised how to turn phones into explosive devices that can avoid detection, according to reports
US officials singled out Apple iPhones and Samsung Galaxy handsets for extra security checks, according to Sky News.
US-bound direct flights from Europe, the Middle East and Africa, have been told to up their security amid fears by US authorities.
Sky News reports: "US security officials said they fear bomb makers from the Yemen-based al Qaeda in the Arabian Peninsula (AQAP) have worked out how to turn the phones into explosive devices which can avoid detection.
"They also are concerned that hard-to-detect bombs could be built into shoes.
"A US official said that other electronic devices carried by passengers also are likely to receive more intense scrutiny."
Aviation security expert Philip Baum told Sky News that heightened security will inevitably mean longer queues and increased waiting times to board flights at UK airports, including random and secondary searches.
