All of the men, whose arrest in August 2006 led to tight restrictions being introduced on carrying liquids on board aircraft around Europe, had denied charges of conspiracy to murder.
Three of the defendants had pleaded guilty to plotting explosions.
Seven also admitted conspiracy to commit public nuisance by distributing al-Qaeda videos threatening suicide bomb attacks in the UK.
Ali and his co-defendants argued that they merely intended to carry out a publicity-style attack to draw attention to their outrage at British and US foreign policy in Iraq and Afghanistan.
They said they never intended to attack aircraft.
The bombs would have been made from liquid explosives based on hydrogen peroxide mixed with an organic component such as tang, a substance used to make soft drinks.
The jury reached its verdict after more than 50 hours of deliberation.
Thousands of international flights from London were affected and liquids were banned from aircraft in 2006 after UK police claimed they had uncovered a plot to blow up planes midway across the Atlantic.