The UK was on maximum terror alert this morning after police said they foiled a terrorist plot to blow up several planes flying between the UK and US.
UK security services said they raised the level of alert to "critical" as airport security was tightened and hand luggage banned from all flights leaving the country.
A host of airlines have suspended flights to London's Heathrow and airports operator BAA PLC has asked National Air Traffic Services to stop all incoming flights that are not already in the air.
Home Secretary John Reid said the alleged terror plot was designed to "bring down a number of aircraft through mid-flight explosions, causing a considerable loss of life".
The plan was uncovered in a joint operation by Scotland Yard's anti-terrorist branch and security services, the Metropolitan Police said.
Police confirmed they have arrested 21 people and are continuing to search a number of properties.
