The Metropolitan Police said late Friday that one of the 24 people was released without being charged.
Police did not identify the person who was released, nor did they say if the person remained a suspect. Twenty-two of the other had their detentions extended through to Wednesday. The final person's detention hearing was delayed until Monday, but the suspect remained in custody.
Travelers in Britain and the U.S. at airports as flight schedules slowly returned to normal.
British police have arrested a total of 24 people suspected of involvement in the plot. CBS News correspondent Sheila MacVicar reports they are all British-born and most are middle class and of Pakistani descent. The youngest is 17. One is a pregnant woman and another is a woman with a six-month old child.
The Bank of England said it had frozen the accounts of 19 of the suspects and, in a very unusual move, posted their names on its Web site.
Pakistani officials said they had arrested five Pakistanis and two Britons in the case, including British national Rashid Rauf, who was arrested about a week ago and described as a "key person" with ties to al Qaeda.
"We arrested him from the (Afghanistan-Pakistan) border area, and on his disclosure we shared the information with British authorities, which led to further arrests in Britain," Interior Minister Aftab Khan Sherpao said. The five Pakistanis were described as suspected "facilitators" of the plot.
Later, a Pakistani intelligence official said 10 Pakistanis had been arrested Friday in the eastern district of Bhawalpur, 300 miles southwest of Islamabad, in connection with the alleged plot. A second intelligence official confirmed there had been arrests but didn't know how many. Both spoke on condition of anonymity because of their sensitive positions.
Also Friday, in a security crackdown after the thwarting of the British airline plot, the Interior Ministry said, without elaborating.
Investigators said the attackers planned to use common electronic devices to detonate liquid explosives to bring down as many as 10 U.S.-bound jumbo jets. Security sources the would-be terrorists discussed blowing their bombs in midair over American cities, maximizing casualties in the air and on the ground, reports MacVicar.
A federal law enforcement official in Washington said that at least one martyrdom tape was found during raids across England on Thursday. Such a tape, as well as the scheme to strike a range of targets at roughly the same time, is a hallmark of al Qaeda.
"There's a lot to suggest to us this is an al Qaeda attack," Frances Townsend, President Bush's homeland security adviser, said on CBS' The Early Show. "We just need a little more time to put together those links."
British Home Secretary John Reid said Britain was grateful for Pakistan's cooperation and that officials believed the main suspects were in custody. However, the threat level in the U.K. remained at "critical," the highest level.
Agents in Pakistan arrested at least seven people, including two British nationals of Pakistani origin who provided information on the terror plot, a senior government official said Friday. The arrests were made in the eastern city of Lahore and in Karachi, the official said on condition of anonymity because he did not have the authority to speak formally on the issue.
Two were Britons arrested about a week ago, he said. The five Pakistanis were arrested on suspicion that they served as local "facilitators" for the two Britons, the official said. It wasn't clear when they'd been detained.
The Guardian newspaper, citing unidentified British government sources, said after the first two arrests were made in Pakistan, a message was sent to Britain telling the plotters: "Do your attacks now." That message was intercepted and decoded earlier this week, The Guardian said.
A U.S. congressman briefed by intelligence officials, who did not want to be identified because of the sensitivity of the investigation, said U.S. intelligence had intercepted terrorist chatter.
Authorities pressed ahead Friday with efforts to smash the purported terror ring. Two U.S. officials said British, U.S. and Pakistani investigators were trying to trace the steps of the suspects in Pakistan and determine whether some of them attended terrorist training camps there.
Police would not say where the suspects were being held — which is not unusual in highly sensitive cases — but terrorist suspects are usually brought to the high-security Paddington Green police station, in central London.
British law permits terrorist suspects to be interrogated for up to 28 days without being charged, although after the first 48 hours court permission is required for further detention.
Meanwhile, airline passengers in Britain and the U.S. faced a second day of disruptions and disappointment as airports struggled to restore flight schedules.
"It is going to be another difficult day today, both for airports and for passengers, but there is cause for optimism that we will get more flights off today," said Stephen Nelson, chief executive of British Airports Authority, which runs Britain's major airports.