LONDON — Three young Britons were declared guilty Monday of planning to blow up trans-Atlantic planes in an al-Qaeda-inspired terrorist plot that could have killed thousands of people and that sparked worldwide changes in airport security.
A jury in London’s Woolwich Crown Court convicted Abdulla Ahmed Ali, 28; Tanvir Hussain, 28; and Assad Sarwar, 29, of conspiring to murder by setting off liquid bombs smuggled aboard North America- bound airliners in sports- drink bottles.
Police have said that the plot was possibly days away from fruition when the men were arrested in August 2006 amid the biggest counterterror-ism investigation in British history.
The verdicts came as a major relief for law-enforcement and intelligence officials stung by the failure of a jury to reach a decision on those charges in the first trial of the men a year ago.
At that time, the suspects were convicted only of conspiracy to murder, without the aircraft element.
“This case reaffirms that we face a real and serious threat from terrorism,” British Home Secretary Alan Johnson said. “This was a particularly complex and daring plot which would have led to a terrible attack resulting in major loss of life.”
But the prosecution’s victory was a partial one.
Four other defendants were acquitted of the same charges Monday, and the jury deadlocked over an eighth man.
The case has shocked the public here not only because of the audacity and scale of the plan but also because its orchestrators were Muslims who were born and raised in Britain but seduced by violent Islamic radicalism.
Revelation of the plot also threw the international airline industry into chaos, with security lines ballooned.
Although many restrictions have been eased, a limit on carry-on liquid items remains in force at many airports and is unlikely to be relaxed.
In the retrial, which lasted nearly six months, prosecutors drew on 26,000 exhibits — including evidence gleaned from a bugged house and seized computers — to detail a plot to bring down seven airliners in a single day.
The organizers allegedly picked out flights from London’s Heathrow Airport to cities such as San Francisco, New York, Washington and Toronto.
Intelligence officials say that the plotters had ties to al-Qaeda and that their handler was a militant based in Pakistan.
The hoped-for high death toll and the targeting of airliners were al-Qaeda hallmarks, as was the involvement of a Pakistan-based explosives expert who masterminded the July 7, 2005, attack on London’s transport system, anti-terrorism officials say.
Those bombings killed 52 people.
