Detectives were applying for more time to question suspects in the alleged airliner bomb plot last night as a series of scares renewed security fears.
There were dramatic scenes in the US after a mid-air "passenger disturbance" on a Washington-bound flight from Heathrow forced the pilot to declare a security emergency.
The United Airlines flight had to be escorted into Boston by two F15 fighter jets, amid claims of a confrontation between a female and flight crew.
In Britain, questions were being asked after two apparent security breaches at Gatwick airport during a period of heightened alert.
The alerts came as Britain's airports finally began to return to normal, almost a week after police foiled an alleged plot to blow up transatlantic passenger jets with liquid based explosives in hand luggage.
However, despite the easing disruption, British Airways still cancelled 35 flights at Heathrow and 11 at Gatwick.
It emerged 20,000 passenger bags went astray at Hea-throw since the start of the disruption.
In closed court hearings last night, anti-terror detectives were applying for more time to question 23 of the 24 suspects in custody over the alleged plot. Officers were presenting evidence to a district judge for him to decide whether it was sufficient to warrant further detention.
The complexity of the case means if detectives are successful, they are likely to seek further extensions - taking them close to the maximum 28 days - before deciding whether to charge or release suspects.
The terror crisis was discussed by Home Secretary John Reid today at a Home Office summit with his European counterparts.
The threat to the European Union and the wider world was "unconstrained in its evil intention," Mr Reid said. "Given the means of destruction on a massive scale which is available through modern technology and biological, chemical and other means, (it) is virtually unconstrained in its capacity and its ability to do immense harm, death and destruction," he added.
The Home Secretary spoke of an "intolerant, violent totalitarianism" that sought to destroy the values of democracy, human rights and justice by "subverting a religion whose very name stands for peace".
Mr Reid also hit back at Conservative leader David Cameron for his outspoken attack on the Government's counter terrorism strategy. He labelled his remarks "disappointing and ill judged".
Mr Cameron had earlier defended his speech - which shattered the political consensus over the terror crisis - describing the reaction as "rather hysterical".
There were also claims yesterday that Britain is seeking the fast-track extradition of another suspect in the case, who is being held in Pakistan.
Rashid Rauf, a British citizen and the brother of one of those held in the UK, is alleged by the Pakistani authorities to have been a key player in the plot and to have links with al Qaida.
However, Rauf's relatives in a remote Pakistani village have insisted he was "harm-less and polite".
The Home Office was still refusing to say whether it had requested extradition. As there is no bi-lateral treaty, Britain would have to make a one-off request. n A care home boy who boarded a plane without a ticket or passport was yesterday under increased supervision, said a social services watchdog.
The 12-year-old took a train to Gatwick after running away from a privately-run resident ial unit in Wirral, Merseyside.
He managed to pass through security checks, despite the terror alert, and board a 6am Monarch Airlines flight to Portugal on Monday.
Staff only realised the boy was a stowaway after he had sat down and been served with a soft drink.
The plane had not taken off and he was escorted from it by police officers.
The boy had been placed into the un-named residential unit by Wigan Metropolitan Borough Council, which was responsible for his care.
A spokesman for the council said: "He was in our care and we had placed him in a children's home on the Wirral.
"He is not permanently confined to the home and the police were alerted as soon as it was realised he had absconded."