By ROBERT BARR
The Associated Press
Authorities downgraded Britain's terror threat level Monday, offering hope to travelers mired in chaos at airports since security forces foiled an alleged plot to bomb packed trans-Atlantic jetliners. But more flights from London were canceled on the fifth day of the crisis.
The threat level was lowered from critical to severe to reflect an intelligence assessment that a terrorist attack remained highly likely but was no longer imminent.
The critical level was declared last week when police rounded up two dozen people suspected of involvement in the terror plot. Police questioned all but one of the suspects Sunday, but authorities remained silent on what, if anything, they learned.
"I want to stress ... that the change in the threat level does not mean that the threat has gone away," Home Secretary John Reid said.
"There is still a very serious threat of an attack. The threat level is at severe, indicating the high likelihood of an attempted terrorist attack at some stage, and I urge the public to remain vigilant," he added.
Those sentiments were echoed across the Atlantic by Homeland Security chief Michael Chertoff, who said Sunday there was a risk that other groups might try to cause bloodshed on the false assumption that law enforcement and intelligence services might be distracted.
He also called for taking a renewed look at U.S. laws that could give authorities the flexibility to detain suspects for longer periods of time. Britain recently passed controversial legislation giving the government up to 28 days to hold terror suspects without charge, and the jetliner plot is the first major test of how those new powers will be used.
With the reduction in the threat level, Britain's Department of Transport said passengers would be allowed to carry a single, briefcase-sized bag aboard aircraft, and that books, laptop computers and iPods would be permitted again. However, Heathrow and other major airports said they would not adopt the relaxed regulations until Tuesday.
British Airways, the dominant carrier at Heathrow, said it canceled a fifth of its flights there Monday. That was down from about a third of flights canceled at Heathrow over the weekend, but passengers faced continued frustration.
Ivana Djak, 16, a student from Columbia, Md., said she slept on her luggage Sunday night, using rolled up T-shirts for a pillow. "It was freezing," she said.
Henry Burkett, 19, a student from Seattle, said he stood in line for three hours Saturday to check his luggage before his flight was canceled 20 minutes before its departure time.
"They don't know where my luggage is at. Maybe in Seattle," he said.
Meanwhile, a British Airways plane en route to New York returned to London after a cell phone on board began to ring and no one admitted owning it. The flight resumed after security checks, and arrived about seven hours late in New York.
Paul Marston, a British Airways spokesman, said the fact that the no one could explain how the phone got on the flight made the situation particularly suspicious. Cell phones — along with all other electronic devices — had been banned from cabins on flights out of Britain since Thursday.
London's anti-terrorist police pressed ahead with a major search in a woodland area in High Wycombe, about 35 miles west of London, said a police official speaking on condition of anonymity. The search would continue for at least 24 hours, though officers declined to say in anything significant had been discovered.
Meanwhile, a court hearing was expected later in the day to determine if officers would be granted more time to question one of the 24 suspects arrested last week.
On Friday, a judge sanctioned extending the custody of 22 other suspects, who can be held until Wednesday for questioning. One suspect was released.
Police arrested the suspects in raids across England on Thursday, saying they had thwarted a plot to blow up as many as 10 passenger planes flying between Britain and the United States. One suspect was released without charge, and a court will decide Monday on the detention of another.
An additional 17 people were detained in Pakistan, including Rashid Rauf, a British national named by Pakistani intelligence as one of the key suspects. Rauf was picked up along the Pakistan-Afghanistan border and is believed to have connections to a senior al-Qaida leader in Afghanistan.
In Kabul, Afghanistan's Foreign Ministry on Sunday denied any Afghan connection to the plot, saying the country — home to thousands of NATO and American troops — was no longer a safe place for al-Qaida to operate.