A schedule displays flights as cancelled at Terminal One Heathrow Airport on August 10, 2006 in London.
A schedule displays flights as cancelled at Terminal One Heathrow Airport on August 10, 2006 in London. - 

TEXT OF STORY

SCOTT JAGOW: If you're flying anywhere today, expect delays and new security measures. The Department of Homeland Security has issued its highest alert for the first time. It applies to flights from Britain to the United States, but all flights in and out of the US are under tighter scrutiny. That's because authorities in London arrested 21 people today. There were no arrests in the US, but the government says it can't be sure this threat is over. Our Correspondent Stephen Beard has more on the story from London.


STEPHEN BEARD: The drama began to unfold early this morning. Britain's Home Secretary John Reid revealed the UK authorities have uncovered what they believe was a major terrorist plot.


JOHN REID: The police acting with the security service MI5 are investigating an alleged plot to bring down a number of aircraft through mid-flight explosions causing considerable loss of life.

The plan says Scotland Yard, was to commit mass murder on an unimaginable scale. The conspirators were allegedly planning to smuggle explosives in hand luggage on board flights bound from the UK to the US.

David Learmount is an aviation security analyst.

DAVID LEARMOUNT: These people obviously had some equipment which actually was onboard detonation equipment of the type possibly that needed manual detonation.

Britain's security agency MI5 raised its threat assessment to the highest level. Security was massively stepped up at every airport in the country.

For the first time in British aviation history, all hand luggage has been banned. Passengers are not allowed to bring anything other than their passports and wallets with them into the cabin. Liquids especially are prohibited except baby milk and that has to be tested in front of security officials.

Analyst Dan Plesche:

DAN PLESCHE: There was an attempt to attack several plans simultaneously perhaps using liquid explosives in things like shampoo or something like that by way of trying to conceal the explosives from the normal forms of detector.

Thousands of passengers arriving to take flights from UK airports were suddenly required to check in their handbags and submit to closer personal searches. Huge lines developed, flights were delayed and then cancelled. Hardly surprising at Heathrow, one of the busiest airports in the world says aviation consultant Derek Jewsen.

DEREK JEWSEN: The 186,000 people planned to go through Heathrow today, to actually mount the sort of extra security is just not feasible. They can do the best that's possible, it's just not adequate.

All the major European carriers have suspended their flights into the UK. The number of long-haul flights out of Britain has been dramatically reduced. Hundreds of Americans have been stranded here. Among them, this young woman.

AMERICAN TRAVELER: When we got to the lobby and listened to the TV a little bit longer, it was quite obvious it was just a madhouse over there and very congested and possibly not even safe to even try to fly out today.

British government officials say the security will remain high until they're satisfied the immediate threat has passed. The disruption could last for several days.

In London, this is Stephen Beard for Marketplace.

SCOTT JAGOW: Just to be clear, no liquids can be carried on any flights in the US as of this morning.

Besides jamming up airports around the world, this is also affecting the markets. Shares of airlines and travel companies plummeted in European trading. American Airlines fell almost 13 percent.