Airline passengers will still face stringent security curbs on what they can carry in hand baggage despite yesterday’s terror-trial verdicts.

The Department for Transport made clear last night that there would be no relaxation of measures that banned most fluids and have forced passengers to remove shoes, jackets and belts before passing through security arches at airports.

Although there is widespread scepticism that “liquid bombs” could bring down a transatlantic airliner, the FBI has provided the British Government and airline industry with evidence of the carnage that would be caused by such devices.

Several months after the alleged plot was discovered in August 2006 the FBI replicated the explosive recipe the men were accused of preparing and deployed it to devastating effect on a disused airliner in a desert air-field. The detonation, filmed from a range of angles, ripped through the fuselage. Had such a blast occurred in mid-flight, the aircraft would have plunged to earth.

The results of the experiment were shared with airline security officials around the world and reinforced the British authorities’ insistence on strict checks on hand baggage and limits on liquids in luggage.

Last night a Department for Transport spokesman dashed any hopes of easing security at airports and on board aircraft. He said: “We base our rules on the Joint Terrorism Analysis Centre’s (JTAC) latest assessment. The current national threat level remains at “severe” which is defined as an attack is highly likely. The court case has proven that a generic capability exists to create liquid bombs from domestic items.”

He added: “Aircraft could be vulnerable to such devices so we are right to continue to require restrictions for liquids carried as hand luggage. We are also right to require these restrictions internationally as, potentially, we are all at risk. Meanwhile, we continue to work with international colleagues to develop technological detection methods which could ease the restrictions.”

BA and British Midland refused to comment when asked whether they thought restrictions should be relaxed. Virgin Atlantic said: “It doesn’t seem likely that these measures will be taken out – flying has changed for what looks like for ever.”

The most stringent security curbs imposed immediately after the alleged plot was discovered were eased later but millions of travellers now expect body searches and know that they may carry only small amounts of liquid, gels or paste in hand baggage.

At first passengers were not allowed to take any hand luggage on board but this was relaxed to allow passengers to carry one piece of baggage of a certain size into the cabin.

An initial ban on pastes, gels and liquids was also eased later to the current allowance. Passengers can currently carry gels, pastes and liquids in bottles of 100 millilitres or smaller. They must be in a clear plastic bag. The rule on only one piece of cabin baggage has been relaxed too, but this depends on the airline.

Extra security measures have cost millions of pounds, as airports bought new security equipment and hired more staff.

At BAA’s airports there are almost 60 additional security lanes and 2,400 new security officers, of whom 1,200 are based at Heathrow.

New X-ray screening machines enable security staff to see a double rather than single image of luggage: one from above and from the side of baggage.

BAA said all queuing time at Heathrow in July was under ten minutes and that 98.5 per cent was under five minutes.

A BAA spokeswoman said: “We are also working closely with airlines and the Department for Transport to take advantage of improvements in security technology and have introduced state of the art technology to all our airports. We are also trialling body scanning technology and iris identification techniques in immigration, all with the aim of improving our service to passengers.”

With the prospect of even more hi-tech security measures at airports, airlines say people have adjusted to the new regime.

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