The threat has been taken so seriously it came close to leading to an outright ban on all hand luggage, a senior insider has revealed.
Mobile phones and electronic devices could still be banned from plane cabins, with the threat of a 9/11-style coordinated attack on London and other major cities feared imminent.
The warning comes as Whitehall officials admit that a terror strike on the UK is now “almost inevitable” particularly with British jihadis returning from fighting alongside the Islamic State in Iraq and Syria.
An airport security source told the Sunday Express: “We’ve been told that five planes are being targeted in a high profile hit before Christmas. They’ve been waiting for the big one.