The threat to the United Kingdom posed by terrorism has been downgraded from critical to severe, the British Home Office has confirmed.
The chaos gripping Britain's aviation industry began to ease tonight after the official terrorist threat level was lowered from its most critical rating.
Four days after police and MI5 smashed an alleged plot to blow up transatlantic passenger jets and stringent security checks were introduced, the threat level was reduced a notch from critical to severe.
That prompted a slight relaxation of the security regime at Britain's airports in a bid to ease the congestion endured by thousands of passengers since last Thursday's anti-terror raids.
However, the new regulations still leave Britain with one of the strictest pre-flight security routines in the world and much tighter constraints on the size of hand luggage.
British Home Secretary John Reid and Transport Secretary Douglas Alexander said the measures were necessary because there was still a "very serious" risk of a terror attack, despite the downgraded threat level.
The severe rating meant an attack was still high likely, but no longer imminent, Mr Reid explained.
Detectives investigating the plot, in which the suspects allegedly planned to explode liquid-based explosive devices smuggled in hand luggage while in mid-flight, were continuing to question 23 people tonight.
They were also conducting searches at several locations linked to the investigation, code-named Operation Overt.
Specialist officers were combing woodland at King's Wood in High Wycombe, Buckinghamshire, close to the scene of one of last Thursday's raids.
However, Scotland Yard remained tight-lipped amid unconfirmed claims that police had found a rifle and a handgun and "suspicious" components during the searches.
Meanwhile in Westminster, Community Secretary Ruth Kelly said the Government and Muslim communities both had to do more as they step up the "battle of hearts and minds" against Islamic extremism.
Speaking after more than three hours of talks with Muslim community leaders Ms Kelly acknowledged there were "different views" over aspects of Government policy.
But there had been a series of "sharp and challenging exchanges" which had been "very constructive and forward looking", she said.
At Heathrow airport tonight, BAA's chief executive Tony Douglas said the airline industry had faced a "national security challenge" on an "unprecedented scale" in the past few days.
He said the situation was becoming more stable, with improved punctuality of flights at Heathrow - the worst affected airport - and fewer cancellations.
Elsewhere, there was still confusion among passengers and anger from some airlines over airport operator BAA's handling of the crisis.
The new security regime will see:
- All liquids banned, except prescription medicines and baby milk;
- The quantity of hand luggage slashed by around 50%;
- Half of all passengers searched.
The official threat level was raised to critical for the first time last week amid fears that the police operation to smash the alleged airliner bomb plot could provoke a retaliatory terrorist strike.
There were also concerns that others linked to the plot may have evaded arrest.
It was downgraded overnight after intelligence experts at the Joint Terrorism and Analysis Centre (JTac) decided that the immediacy of the threat had passed.
At an early morning news conference, Mr Reid denied that the lowering of the threat level was based on "commercial" pressures and said the decisions were based on the analysis of independent intelligence experts, and not ministers.
However, he said: "Threat level assessments are intelligence-led. It is not a process where scientific precision is possible, They involve judgments."
Agencies