The 37-year-old French citizen of Moroccan descent pleaded guilty to conspiracy in connection with the attacks, in which hijacked airliners were flown into buildings in New York City and Washington DC killing nearly 3,000 people.

Prosecutors had called for the death penalty for Moussaoui, but the jury at his 2006 trial rejected the government’s case for execution as not all jurors were convinced he had a significant role in the attacks.

Moussaoui, who during the course of the trial made conflicting claims stating that he was either to hijack a fifth airliner on September 11 or stage another attack after the date, was in jail on immigration charges when the attacks took place.

He had been arrested several weeks before September 11 after raising suspicions at a Minnesota flight school.