BBC News
 

London, Aug 10: A terrorist plot to blow up planes in mid-flight from the UK to the US has been disrupted, Scotland Yard has said.

It is thought the plan was to detonate explosive devices smuggled on aircraft in hand luggage.

Police have arrested about 18 people in the London area after an anti-terrorist operation lasting several months.

Security at all airports in the UK has been tightened and delays are reported. MI5 has raised the UK threat level to critical - the highest possible.

According to MI5's website, critical threat level means "an attack is expected imminently and indicates an extremely high level of threat to the UK".

BBC home affairs correspondent Daniel Sandford says he does not think the police believe an attack is imminent.

"The reason for raising the threat level is in case there is some other sub-plot, back-up plot around this that the police aren't aware of," he said.

Scotland Yard said in a statement that their investigation into the alleged plot was a "major operation" which would be "lengthy and complex".

"We would like to reassure the public that this operation was carried out with public safety uppermost in our minds."

Home Secretary John Reid confirmed that there had apparently been a plot "to bring down a number of aircraft through mid-flight explosions causing a considerable loss of life".

Prime Minister Tony Blair is on holiday in the Caribbean, but Downing Street said the police operation was undertaken with his full support and he had been "in constant touch".

A spokesman for Number 10 added that Mr Blair had briefed US President George Bush on the situation during the night.

The Department for Transport set out the details of the security measures at UK airports.

The current threat level is assessed as critical as of 10th August 2006 - this means that an attack is expected imminently and indicates an extremely high level of threat to the UK

Passengers will not be allowed to take any hand luggage on to any flights in the UK, the department said.

Only the barest essentials - including passports and wallets - will be allowed to be carried on board in transparent plastic bags.

"We hope that these measures, which are being kept under review by the government, will need to be in place for a limited period only," the statement said.

At Heathrow Airport, BBC presenter Fiona Bruce said there were "ranks of people" unable to get into the terminal.

"Terminal One is completely at a standstill. Nobody is being checked in at all."

 
Passengers have to put any carry-on luggage in plastic bags

She said it was "jam-packed", but passengers were managing to remain "good natured".

BBC journalist Joe Lynam encountered the increased security measures at Gatwick airport.

"I was handed a piece of paper saying that pretty much nothing could be taken on board the plane," he said.

"Everything had to be checked in and that includes mobile phones, ipods, wallets - even spectacle cases had to be checked in."

British Airways said that passengers who do not wish to fly on Thursday can rebook on flights leaving over the next two weeks.

David Learmount from Flight International Magazine said he expected passengers to be searched much more carefully.

He added: "This is the first time this measure has actually been taken. Certainly I've never seen hand luggage banned."