Police have been given extra time to question 23 of the alleged plane plot suspects, while a US-bound flight has been diverted after a claustrophobic passenger caused a security alert.

Two American fighter jets escorted the plane to Boston after the disruptive woman prompted the pilot to declare an on-board emergency.

When police searched the 60-year-old passenger, they found a pot of hand cream missed by airport staff at Heathrow. She also carried some matches, which are allowed on board.

The luggage of all 182 passengers on United flight 923 was laid out on the tarmac at Boston's Logan International Airport and checked by sniffer dogs.

The failure at Heathrow to detect the cream is the latest security lapse at a British airport. At Gatwick, an inquiry is also underway as to how a 12-year-old boarded a flight to Portugal without a passport or ticket.

In another Gatwick incident, a man smashed an alarmed glass door at one of the berths to go back and look for his missing wallet.

All liquids and gels are banned on flights from Britain to America, following the alleged plot to blow up transatlantic aircraft with liquid explosives hidden in hand luggage.

A United spokesperson confirmed there was a confrontation between a woman and crew on the diverted plane, originally destined for Washington. She was arrested for interfering with a flight.

Closed extension hearings

Meanwhile a judge has given permission for 21 of the terror suspects arrested in Britain last week to be questioned until August 23, the Met police confirmed last night. Another two can be held until August 21.

One person, arrested on Tuesday in the Thames Valley, was released without charge.

In closed hearings yesterday, officers presented evidence to a district judge to decide if each case warrants further detention. The suspects, held at central London police stations, were not allowed to make representations and were told of the court's decision via videolink.

Police are expected to seek a series of further extensions, to a maximum of 28 days, before bringing charges.

In an interview with Channel 4 News, the brother of Assad Sarwar, one of those arrested in High Wycombe last week, was "an innocent guy".

Amjad Sarwar said his brother had abandoned his studies and became increasingly religious, but was no terrorist.

"There is no way he could have anything to do with terrorism. He condemns terrorism. He's always talking about bin Laden being a terrorist and the Iraq war: they're all terrorists. So he condemns all that.

The 23 suspects were rounded up last Thursday in raids across London, High Wycombe in Buckinghamshire and Birmingham. Since then, detectives have raided 46 homes and businesses and seized about 20 vehicles.

Officers are still searching 22 premises, including woodland in High Wycombe where bomb-making equipment has reportedly been found.

Al-Qaida 'mastermind'

In Pakistan, at least 17 suspects are in custody, including the Briton Rashid Rauf. The Home Office would not confirm whether it has asked for his extradition.

Pakistani security sources have said al-Qaida's "number three", Abu Faraj al-Libbi, was the brain behind the alleged terror plot, the daily newspaper Dawn reported.

"There was a mastermind, there was a planner, and there were the executioners," an unnamed official told the paper.

Al-Libbi is now in US hands after being arrested last year over an alleged plot to assassinate Pakistan's president Pervez Musharraf.

Most British airports have returned to normal after last week's travel chaos. At Heathrow, British Airways (BA) has cancelled 19 flights today, while Gatwick, Stansted and Luton are fully operational.

BA is still trying to reunite 5,000 pieces of lost luggage with their owners. (See full story.) Hand luggage is still restricted to one small bag per passenger, about the size of a laptop case.

Tighter security will be introduced at airports across Europe, interior ministers from across the continent decided at a meeting in London yesterday.

"The events of last week demonstrated that terrorist groups are constantly seeking new ways of attacking our societies," said home secretary John Reid, who co-hosted the meeting.

"My colleagues know that their citizens face the same threat that we do and today we stood shoulder to shoulder in our determination to fight it."