A Spanish court has sentenced Syrian-born Imad Yarkas to 27 years for conspiracy to commit murder in connection with the 11 September attacks in the US.
Yarkas is said to have found recruits in Spain for al-Qaeda
He was also convicted being a member of a terrorist organisation.
Prosecutors had hoped to jail Yarkas for 25 years for each of the 2,973 people killed in the 2001 attacks.
But he was found guilty of the lesser charge of conspiracy and given 15 years. He received another 12 for
leading a terror organisation.
Yarkas, 42, also known as Abu Dahdah, is said to have recruited and indoctrinated candidates to be sent for military training in Afghanistan.
Along with co-defendant Driss Chebli, Yarkas is said to have set up a meeting in July 2001, which was allegedly attended by Mohamed Atta - the attacker who piloted one of the hijacked planes into the Twin Towers - and Ramzi Binalshibh, another top 9/11 suspect who has been in US custody since being arrested in Pakistan in September 2002.
Chebli, who had also faced the full multiple murder charges, was sentenced to six years for collaboration.
Yarkas described himself as a businessman dealing in second-hand cars. He was arrested in November 2001, about four years after Spanish police began tapping his telephone.
His number was found by German police in the Hamburg flat believed to have been used by two of the hijackers - including Mohamed Atta. Atta's phone number was also found in Yarkas' European contacts, according to investigating Judge Baltasar Garzon.
Two weeks before the 11 September attacks, Yarkas is said to have received a phone call in which a man called "Shakur" - later identified as Farid Hilali - told him in cryptic language: "We've entered the field of aviation, and we've even cut the throat of the bird."
This was taken to be a reference to the final stage in preparing the attacks - even though the US commission that investigated the 11 September events found no evidence to link "Shakur" to the plot.