Three British Muslims have been convicted of planning a series of co-ordinated suicide bomb attacks on transatlantic airliners, which could have killed up to 10,000 people.
The al-Qaeda cell plotted to cause mass murder by detonating home-made liquid explosives on board at least seven passenger flights bound for the US and Canada.
The plot had the potential to be three times as deadly as the 9/11 attacks of 2001.
The convictions followed Britain’s largest counter-terrorism operation and two criminal trials which, in total, cost an estimated £60million.
All three men convicted on Monday had been found guilty at an earlier trial last year of conspiracy to murder, but prosecutors said it was vital to secure a conviction on another charge of conspiring to blow up the aircraft in order to prove that the threat to air traffic was genuine.
Their arrests in 2006 resulted in immediate worldwide restrictions on passengers carrying liquids in their hand luggage. A ban on containers larger than 100ml is still in place.
When the men were arrested, one of the plotters, Abdulla Ahmed Ali, had a computer memory stick in his pocket which highlighted seven flights from London to six cities in the US and Canada, each carrying between 241 and 286 passengers and crew.
The flights all departed within 2 hours and 35 minutes of each other, to Chicago, Montreal, Toronto, San Francisco, Washington and New York and police believed there would have been no chance of stopping the attacks once all the aircraft were in the air.
Investigators also believed that the men were considering an even larger attack after they were bugged discussing plans for as many as 18 suicide bombers, which could have led to 5,000 deaths in the air and as many again on the ground.
The case has also led to a review of visa restrictions on Britons travelling to the US, and yesterday’s convictions, which came during the diplomatic row over the release of the Lockerbie bomber, focused yet more attention in the US on how Britain deals with terrorists.
Ali, 28, Assad Sarwar, 29, and Tanvir Hussain, 28, were found guilty of conspiracy to murder by detonating bombs on airliners at the end of a six-month trial at Woolwich Crown Court in London.
A jury at their previous trial had failed to reach verdicts on whether such a plot existed.
The men made suicide videos, and they were bugged by MI5 which revealed how they discussed details of the plot.
They were also filmed in their bomb factory in east London where they had practised making bombs from household goods, including soft drink bottles, batteries and disposable cameras.
But new evidence was put to the jury at their retrial in the form of a series of emails in which the men used code words to discuss their plans with an al-Qaeda fixer based in Pakistan.
The emails and conversations suggested that the plot was in its final stages, possibly days away from execution.
MI5 believed the plotters were linked to the highest levels of al-Qaeda through a British man called Rashid Rauf, who was also involved in the build-up to the attacks of July 7 and July 21 2005.
Rauf was reported to have been killed by an unmanned drone in Pakistan last year but senior security sources have told The Daily Telegraph that he may have survived
The jury found a fourth man, an Islamic convert called Umar Islam, 31, guilty of conspiracy to murder, but could not decide if he knew about the plan to blow up aircraft.
Three others, Ibrahim Savant, 28, Arafat Waheed Khan, 28, and Waheed Zaman, 25, were acquitted of the airlines plot but the jury could not decide if they were guilty of conspiracy to murder.
The Crown Prosecution Service must now decide whether those men, who were also tried last year, should face a third trial.
An eighth man, Donald Stewart-Whyte, 23, was acquitted of all charges.
Six of the eight men, most of whom were British-born and university educated and three of whom were converts, had recorded fiery videos that blamed the West for the slaughter of Muslims and promised floods of martyr operations in return.
Security sources have called the investigation the most significant since the Second World War.
Ali, from Walthamstow, east London, was described in court as the leader who was able to identify in other Muslims a kindred spirit or vulnerability while Sarwar, from High Wycombe, Bucks, was the bomb-maker and Hussain the quartermaster, helped to prepare the bombs.
The others were described as foot soldiers ready to respond when the time was right.
Deputy Assistant Commissioner John McDowall, head of the Metropolitan Police’s Counter Terrorism Command, said the men intended to commit “mass murder on an unimaginable scale”.
“If these terrorists had been successful, many people would have lost their lives. Many more would have died if they had chosen to detonate their bombs over land,” he said. “But their plans were thwarted by the police and security services.”