"We affirm Moussaoui's convictions and sentences in their entirety and deny his motion to remand," the opinion filed Tuesday in the 4th U.S. Circuit Court of Appeals in Richmond, Va., said.
The unanimous opinion said the three-judge panel wasn't persuaded by any of the arguments challenging the fairness of the proceedings.
In 2005, Moussaoui pleaded guilty to six conspiracy counts in al-Qaida's plot to use airplanes to commit terrorist acts on the United States. During sentencing, the jury imposed a prison sentence of life without possibility of parole.
In his appeal, Moussaoui challenged the validity of his guilty plea and his sentences, the 77-page opinion said. He also has filed a motion to remand the proceedings, based on the government's revelation of classified information during the appeals process.
Moussaoui, the so-called 20th hijacker, was arrested for staying in the United States on an expired visa, raising suspicions of instructors at a flight school in Eagan, Minn., where he was being trained on a jet stimulator. He was in jail when the terror attacks occurred in New York and Washington, and passengers forced another airliner to crash in Pennsylvania.