Four other men were found not guilty of the plot and the jury failed to reach a verdict in the case of an eighth suspect.
The conspirators were caught just days from putting the plan into operation following the largest surveillance operation of its kind being carried out by British police.
"If they had been successfully deployed, they would have killed thousands of people on board and maybe more if they had detonated them over land," said a senior British police source, speaking on condition on anonymity.
Speaking to Al Jazeera, Steve Park, a terrorism and security analyst, said: "The US were forcing their hand in saying to the British government, 'We need to get these people arrested', that's how strong the evidence was.
"I think it will be considered a landmark case, the British government obviously thought that the evidence was overwhelming to arrest anybody suspected within the conspiracy theory world because it's so difficult to get a conviction in the final event."
US officials have said the carnage would have been on the same scale as the September 11, 2001 attacks on New York and Washington that killed 3,000 people.
Prosecutors said the plot centred on seven flights from Heathrow's Terminal 3, each capable of carrying between 241 and 285 passengers.
But recorded conversations between some of the men, British Muslims aged in their 20s at the time, suggested other terminals and possibly 18 suicide bombers might have been involved, while targets such as gas terminals and oil refineries were mentioned.
The plot was hatched in Pakistan just months before the men were arrested in August 2006.
Police suspect that al-Qaeda planner, Egyptian Abu Obaidah al Masri, who some media reports have cited as the inspiration for the deadly July 7, 2005 suicide bombings in London, was the mastermind.
The British ringleader was Ali, 28, while Sarwar gathered the bomb ingredients at his home in High Wycombe, a town west of the capital.
At a previous trial last year, Ali, Sarwar and Hussain were found guilty of conspiracy to commit murder but the jury failed to agree on whether they had intended to blow up planes.
They will be sentenced at a later date.