Police were granted extra time last night to question nine suspects in custody over the alleged airline bomb plot, Scotland Yard said.
A High Court judge sitting at City of Westminster Magistrates' Court in central London granted officers an extra week to hold eight suspects.
The ninth, Umair Hussain (24) from east London, had custody extended for 24 hours.
An 11th is still being held, Scotland Yard said.
A Metropolitan Police spokesman said: "In all operations some may be released without charge while others remain in custody. This is not unusual and is to be expected in large and complex criminal inquiries with a number of arrests."
The judge's decision means officers can hold eight of the suspects until August 30, and Umair Hussain until tonight. Police can apply for a further week's custody next Wednesday.
Tim Rustem, Umair Hussain's solicitor, said he was pleased the judge rejected a police application to hold his client an extra week.
He said it was "a big victory", adding: "It is a new system and we are all coming to terms with it.
"It is good to see it works, where a High Court judge can in some cases grant the full seven days but at the same time use discretion where, for example, it's only a circumstantial case."
Mr Rustem said he was "optimistic" his client would be released without charge.
He added Hussain - one of three brothers arrested - was "quite upset" about the way police treated him and wanted to speak out after his release.
Detectives investigating the alleged plot began searching a second area of woodland in Buckinghamshire yesterday.
Officers are searching Booker Common, the other side of High Wycombe from King's Wood, which police have combed for days.
This week Peter Clarke, head of Scotland Yard's Anti-Terrorist Branch, disclosed details of the "immense" scale of Operation Overt.
He said police seized bomb-making equipment, including chemicals such as hydrogen peroxide, electrical components and documents.
Officers recovered martyrdom videos, 400 computers, 200 mobiles and 8,000 computer media items such as DVDs and memory sticks.
There had been 69 searches in houses, flats and businesses, vehicles and open spaces, he said.
The alleged plot was to manufacture and smuggle the component parts of improvised explosive devices onto passenger jets and assemble, then detonate them.
At City of Westminster Magistrates' Court on Tuesday, 11 people were remanded in custody.
The defendants included a young mother of an eight-month-old baby, her husband, and a 17-year-old.
In short hearings, eight men, aged between 19 and 28, appeared accused of conspiracy to murder and preparing an act of terrorism. All eight were remanded until September 4, when they will reappear at the Old Bailey for a preliminary hearing.
The remaining three appeared later charged with offences under the Terrorism Act 2000.
Two were remanded in custody until August 29 when they are expected to reappear before the magistrates' court.
The third was also remanded in custody until August 29 but is next expected to appear in person on September 19.
All of the suspects were arrested in overnight raids on August 10.