Could bombs be smuggled onto planes in smartphones? Passengers flying to US to have their mobiles screened as new terror alert travel chaos for holidaymakers

American officials have asked UK airports to bring in stricter checks on electronic devices after intelligence sources warned of a new threat of 'stealth bombs' from Islamic extremists. US experts have identified iPhones and Samsung Galaxy models (inset) as the biggest concern as queues snaked around some of the UK's busiest airports, including Gatwick (right) and Manchester (left).