Zacarias Moussaoui, a member of al-Qaeda commonly referred to as the “20th hijacker,” has accused members of the Saudi royal family of directly funding the terrorist organization that planned and executed the September 11, 2001, attacks.

Moussaoui made the striking claim from inside the federal supermax prison where he is serving a life sentence on terrorism charges. In interviews with lawyers across two days in October but first made public on Tuesday, Moussaoui painted a picture of multi-faceted Qaeda-Saudi relations. He claimed that, tasked with creating a digital record of al-Qaeda’s donors by Osama bin Laden, he entered into the record the names of Prince Turki al-Faisal, Prince Bandar Bin Sultan, and Prince al-Waleed bin Talal. Al-Faisal was then Saudi Arabia’s chief of intelligence, Bin Sultan was a longtime ambassador to the United States, and bin Talal is a billionaire investor perhaps best known to Americans for owning a large stake in News Corp., the company that owns Fox News.

The Saudi royal family immediately rejected Moussaoui’s accusations, noting that he is a convicted terrorist conspirator whose lawyers once argued was mentally unfit to stand trial. “Moussaoui is a deranged criminal whose own lawyers presented evidence that he was mentally incompetent,” a statement from the Saudi government read. “His words have no credibility.”

Moussaoui earned the “20th hijacker” moniker by claiming he was meant to join up with the 9/11 attackers. In a 2006 video, however, bin Laden directly denied that Moussaoui was assigned to the 9/11 group.

In addition to the funding accusations, Moussaoui claimed to have discussed a plot against Air Force One, the presidential aircraft of the United States, with a member of the Islamic Affairs Department of the Saudi Embassy in Washington. Moussaoui said he met with the official in Kandahar, but was arrested before he was able to further the nascent plans.

Moussaoui also testified that he traveled to Saudi Arabia as a courier for bin Laden, and enjoyed luxury air travel and accommodations, as well as in-person meetings with members of the royal family.

The existence of connections between wealthy Saudis and the royal family to al-Qaeda and other terrorist groups has long been a matter of dispute. The 9/11 Commission, convened by the federal government to investigate the attacks, did not find evidence of direct Qaeda funding from the Saudi royal family. It did, however, air the possibility that charities funded by the Saudi government could have diverted money to terrorists.

Senators Bob Graham and Bob Kerrey, who served on the Joint Congressional Inquiry and 9/11 Commission, respectively, filed briefs on Monday in the same lawsuit in which Moussaoui testified. Graham and Kerrey demanded the release of the 28 pages of the commission’s report that remain classified, and rejected the Saudi government’s characterization that the report cleared them of involvement in the attacks.

“I am convinced that there was a direct line between at least some of the terrorists who carried out the Sept. 11 attacks and the government of Saudi Arabia,” Graham wrote.

Moussaoui was testifying in a case brought forth by families of those who died in the 9/11 attacks. The suit had previously been dismissed before being reinstated after an appellate court found Saudi Arabia’s claims of sovereign immunity unsatisfying. Families of victims have been also been suing Saudi Arabian elites for years, in Burnett v. al Baraka, a lawsuit that, as New York Times reporter James Risen revealed in his latest book, Pay Any Price, may have been co-opted—or at least compromised—by United States intelligence services.