The airline plot was broken up when suspects were arrested in raids in London and the surrounding area in August 2006.
The foiled attack grounded hundreds of flights and changed air travel for good with airline authorities putting strict restrictions on the quantity of liquids passengers can carry in their luggage.
The three men convicted on Thursday had faced two previous trials in 2008 and 2009.
A jury at their first trial failed to agree a verdict.
They were acquitted at the second trial of knowing that the plot was targeting planes but prosecutors said they had prepared to become suicide bombers and recorded "martyrdom" videos.
The men had argued that the videos were part of an elaborate publicity stunt.
Prosecutors made the unusual decision to push for a third trial where the three faced a broader charge of conspiracy to murder, replacing the previous charge of plotting to kill people on airliners.
Prosecutor Sue Hemming said the the three men "were involved in a calculated and sophisticated plot to create a terrorist event of major proportions, working alongside others who were determined to bring down aircraft using homemade explosives, causing the maximum possible loss of life".
"They were cleared in the previous trial of being aware of the ultimate targets of the plot, but we say that they were committed to the principle and practice of violent jihad to the point of targeting innocent people in an attempt to further their cause," Hemming said.
Ali and two others were found guilty of the airline bomb plot last year.