Police have disrupted a major plot to blow up as many as 20 planes over UK and US cities with explosive devices smuggled aboard as hand luggage.
Police are have arrested 20 people in London - the culmination of a covert counter-terrorist operation lasting several months.
Big queues were building up at UK airports as passengers trying to board international flights were not being allowed to carry on normal hand luggage.
Security sources are said to be believe that liquid explosives would have been used and could therefore be missed during the x-ray screening of such luggage.
Queues at Heathrow Sky News' Crime Correspondent Martin Brunt said he had been told the threat was imminent and those arrested were mainly young, British-born Asian men.
The Home Secretary John Reid said the alleged plot was a "major threat" to bring down a number of planes.
The Home Office's level of security - indicating public risk - has been raised from 'severe' to 'critical'.
The US government has also raised its threat assessment to the highest level for commercial flights from Britain to America.
Flights have been cancelled Homeland Security Secretary Michael Chertoff said: "We believe that these arrests (in London) have significantly disrupted the threat, but we cannot be sure that the threat has been entirely eliminated or the plot completely thwarted."
In Britain, there have been lengthy queues at most airports with many domestic flights cancelled.
Flights scheduled into Heathrow were cancelled - apart from those already in the air.
Flights to Britain with the German carrier Lufthansa, Spanish airline Iberia and Greek carrier Olympic were cancelled.
The British Airports Authority urged passengers not to go to Heathrow unless absolutely necessary.
:: Security experts said such an attack would have a precedent - during the 1990s, a plot was foiled to blow up 12 Western airliners simultaneously in Asia.
The plot, which would have killed thousands, was scuppered when plans were found in the Philippines base of terrorist Ramzi Yousef who also planned the 1993 World Trade Centre bombing.
Source: www.skynews.co.uk
Police are have arrested 20 people in London - the culmination of a covert counter-terrorist operation lasting several months.
Big queues were building up at UK airports as passengers trying to board international flights were not being allowed to carry on normal hand luggage.
Security sources are said to be believe that liquid explosives would have been used and could therefore be missed during the x-ray screening of such luggage.
Queues at Heathrow Sky News' Crime Correspondent Martin Brunt said he had been told the threat was imminent and those arrested were mainly young, British-born Asian men.
The Home Secretary John Reid said the alleged plot was a "major threat" to bring down a number of planes.
The Home Office's level of security - indicating public risk - has been raised from 'severe' to 'critical'.
The US government has also raised its threat assessment to the highest level for commercial flights from Britain to America.
Flights have been cancelled Homeland Security Secretary Michael Chertoff said: "We believe that these arrests (in London) have significantly disrupted the threat, but we cannot be sure that the threat has been entirely eliminated or the plot completely thwarted."
In Britain, there have been lengthy queues at most airports with many domestic flights cancelled.
Flights scheduled into Heathrow were cancelled - apart from those already in the air.
Flights to Britain with the German carrier Lufthansa, Spanish airline Iberia and Greek carrier Olympic were cancelled.
The British Airports Authority urged passengers not to go to Heathrow unless absolutely necessary.
:: Security experts said such an attack would have a precedent - during the 1990s, a plot was foiled to blow up 12 Western airliners simultaneously in Asia.
The plot, which would have killed thousands, was scuppered when plans were found in the Philippines base of terrorist Ramzi Yousef who also planned the 1993 World Trade Centre bombing.
Source: www.skynews.co.uk
