A Woolwich Crown Court jury convicted Abdulla Ahmed Ali, 28, Tanvir Hussain, 28, and Assad Sarwar, 29, of conspiring to activate bombs disguised as drinks.
Four other men were found not guilty of involvement in the suicide bomb plot.
The arrests in August 2006 caused chaos to international aviation and prompted the current restrictions on liquids.
The jury heard that at the time of his arrest, plot ringleader Ahmed Ali had identified seven US and Canada-bound flights to blow up over the Atlantic within a two-and-a-half-hour period.
They were flights from London's Heathrow airport to San Francisco, Washington, New York, Chicago, Toronto and Montreal. Had the planes taken to the air with bombers on board, there would have been little chance of saving them.
His "quartermaster", Sarwar, had secured bomb ingredients at his home and in woods in High Wycombe, Buckinghamshire. A flat in the Walthamstow area of east London became the bomb factory.
There the men put together a special home-made mixture of chemicals that they planned to take onto planes in ordinary sports drinks bottles stored within hand luggage. Ahmed Ali, of Walthamstow, Hussain, of Leyton, east London, and Sarwar had been found guilty previously of a conspiracy to murder involving liquid bombs.
The jury in that first trial could not decide whether their plans extended to detonating the devices on planes. But a second jury was convinced.
The plot became the biggest terror investigation in the UK and intelligence officers believe it was directed by al-Qaeda figures in Pakistan.
The BBC understands that the key contact for the plotters was a British man, Rashid Rauf, now thought to be dead.
Security officials on both sides of the Atlantic believe the men wanted to kill thousands in the air and possibly more on the ground in a wave of attacks causing more devastation - and political fall-out - than the 11 September attacks.
"This was a particularly complex and daring plot which would have led to a terrible attack resulting in major loss of life.
"The police, security services and CPS have done an excellent job in bringing these people to justice."
Sue Hemming, from the Crown Prosecution Service (CPS), said the plot had been sophisticated and calculated to create a terrorist attack event of "global proportions".
"The CPS is committed to prosecuting to the full extent of the law those who would use terror to try to achieve their aims, whatever their motivation and their perceived justification," she said.
"This trial has been another demonstration of that commitment."
Umar Islam, 31, from Plaistow, east London, was convicted of conspiracy to murder, but the jury failed to reach a verdict on whether he was involved in a plot to blow up aircraft. He, like the ringleaders, faces life imprisonment.
Three others were found not guilty of plotting to bomb aircraft: Ibrahim Savant, 28, Arafat Khan, 28, Waheed Zaman, 25.
The jury failed to reach verdicts on a more general conspiracy to murder charges against Mr Savant, from Stoke Newington, east London, and Mr Khan and Mr Zaman, both from Walthamstow. The CPS has a week to decide whether to try the men for a third time.
An eighth man, Donald Stewart-Whyte, 23, of High Wycombe, was cleared of all charges. His lawyers have called for an inquiry into why the Muslim convert was prosecuted.
The security services installed a hidden camera in the Walthamstow bomb factory and saw both Ahmed Ali and Hussain preparing devices and making arrangements for the jihadist suicide videos, recorded in the same property.
The men's defence was that they had been planning a political stunt, including small explosions intended only to frighten people at airports.
These political demonstrations, they said, would be backed up by a documentary they were making about western injustices.
The videos they had made were part of that documentary, they said. No other material from the alleged documentary was ever uncovered.