British authorities have now arrested 24 people in connection with an alleged plot to blow up U.S.-bound passenger aircraft. Meanwhile, British air traffic, which was thrown into chaos by the revelation of the plot, was slowly creeping back to normality Friday.

Home Secretary John Reid said Friday that 24 people are now undergoing interrogation in London in connection with the alleged terrorist plot. He said all the main players are in custody, but cautioned that the investigation is continuing.

British police officers stand guard outside a cordoned-off house in High Wycombe, England after a massive security operation resulted in a number of arrests across the United Kingdom, Friday Aug. 11, 2006

"The police and the security service believe that we have the main suspects. And, we balance that all the time by saying that this is an ongoing operation. There is no 100 percent certainty with these things," Reid said. "And, we will continue to maintain our vigilance at the highest level, and we will continue to pursue any avenues or evidence that comes before us."

Published reports in both Britain and the United States say that some suspects are still at large.

Reid said the threat level will remain at critical, the highest level in Britain, as a "precautionary measure."

The names of 19 of the suspects were released by the Bank of England when the bank froze their assets. They range in age from 17-34. British and U.S. sources say most of them appear to be young British Muslims.

Evidence of a connection to Pakistan also surfaced, when Pakistani authorities announced the arrests of at least five people in connection with the plot. Home Secretary Reid refused to discuss details of the Pakistani arrests, except to thank Pakistan for its help.

"This was an operation conducted largely in the United Kingdom and driven from here. But, of course, like many other such operations, it has an international dimension," he said. "We are very grateful for all the help and cooperation we have received from our international partners, including Pakistan, and I would like to thank them for the assistance that they have given us."

Authorities believe that the plotters planned to smuggle the explosives aboard as many as 10 aircraft in liquid form, then detonate them as the planes approached U.S. cities. U.S. and British officials say the plan was on the verge of implementation, forcing the police and security services to swoop down on the plotters before they could act.

Britain and the United States immediately imposed stringent new security measures for airlines Thursday, after the public emergence of the plot. The new measures wreaked havoc on aviation worldwide, and especially in London, a major hub for international flights. Air travelers in Britain found themselves waiting in long lines, as they confronted canceled flights and new rules that ban virtually all carry-on luggage from airplane cabins.

British Transport Secretary Douglas Alexander described the situation at British airports as still difficult, but gradually getting better, and thanked the public for its patience and good humor during a difficult period.

"Standing firm in the face of terrorism involves us all," he said. "Sometimes, as in yesterday, it means staying calm at the end of a very long check-in queue [line]. The forbearance that has been shown, and continues to be shown today by the traveling public demonstrates that the worst instincts of a tiny minority has brought forth the best instincts of the vast majority."

Alexander said his department is working on drawing up new security guidelines for British airports that will be workable in a high-pressure environment like Heathrow, one of the busiest airports in the world.