A bombshell account of high-level Saudi Arabian involvement in al Qaeda activities given by a former operative raised ire in diplomatic circles this week. Yet it also underscored the paucity of information concerning the country's ties to terrorism that has been made public by the US government.

In October, French-born Zacarias Moussaoui talked to attorneys for family members of 9/11 victims suing the Saudi government for alleged complicity in the terrorist attack. He told the lawyers that he met with high-ranking members of the royal family, including the current king. This week, his testimony was introduced in the case at a Manhattan court.

Moussaoui, who is suspected of being the possible 20th 9/11 hijacker and currently locked up at the Federal Supermax Prison in Colorado, told the attorneys he was dispatched by Osama bin Laden in the late 1990s to keep tabs on who donated to al Qaeda. That list, he said, included Prince Turki al-Faisal, then Saudi Arabia's intelligence chief and Prince Bandar Bin Sultan, the former Saudi ambassador to the US who was in Washington at the time of the attacks.

Most alarming of his disclosures was an alleged encounter that took place in Afghanistan with an official from the Saudi Embassy in Washington. Moussaoui said the two discussed "the feasibility of shooting Air Force One," the US presidential plane, with a stinger missile.

Much of Saudi Arabia's early involvement with Islamist militants is well known. Like the US, the Saudis supported and financed the mujahideen — who later would seed a nascent al Qaeda — that fought off a Soviet invasion of Afghanistan in the 1980s. Once al Qaeda was formed, it is widely believed the Saudi government essentially paid the group for a number of years in order to ward off attacks inside its borders.

The point at which direct Saudi support for al Qaeda broke off remains one of the lingering questions surrounding the 9/11 attacks. Family members of victims and some members of Congress have long said evidence of such involvement is contained in the 28 pages of a 2002 intelligence report that have remained redacted for 13 years.

In December 2013, House Representatives Walter Jones (R-NC) and Stephen Lynch (D-MA) introduced a resolution calling on President Obama to release the pages, part of the Joint Inquiry into Intelligence Community Activities Before and After the Terrorist Attacks of September 11, 2001. Despite claims from family members that Obama promised to do so, the portion remains classified.

The Saudi government has always denied culpability and itself urged that the 28 pages be made public, a request that was denied by the Bush administration. However, members of Congress who have seen the pages say they show damning intelligence gathered on Saudi individuals. Made public, the redacted portions could prove that the Bush administration knew, perhaps not of a large scale conspiracy emanating from the royal family, but at least of significant Saudi involvement — even as they drew not so subtle links to 9/11 in the lead-up to the 2003 invasion of Iraq.

"The recent testimony by Mr. Moussaoui is further reason to declassify the 28 pages of the Joint Inquiry report," Jones told VICE News. "The contents of the pages do not pose a threat to national security but deal with relations the Bush administration had before 9/11."

Former Senator Bob Graham (D-FL), who was a co-chair of the inquiry, last year told VICE News that the pages included references to the financing of 9/11, and that redacting them amounted to a "cover-up."

In a 2012 affidavit in the case against the Saudi government, Graham went into greater detail. "I am convinced that there was a direct line between at least some of the terrorists who carried out the September 11 attacks and the government of Saudi Arabia," he told the court.

Moussaoui, who was termed mentally ill by a psychologist at his trial, is seen as an erratic, if intelligent, source. Last year, he requested that he be allowed to provide testimony in the New York trial against the Saudi government. In October, federal officials allowed him to do so.

Bruce Riedel, director of the Brookings Institute's Intelligence Project, told VICE News he found it hard to take seriously the entirety of Moussaoui's account, particularly his accusation that the Saudi government wanted to assassinate then president Bill Clinton by shooting down Air Force One. "There are other parts of the story that I can find might make some sense, but once you add that on in, I think it is in the realm of the implausible," he said.

On Wednesday, the Saudi embassy said in a statement: "Moussaoui is a deranged criminal whose own lawyers presented evidence that he was mentally incompetent. His words have no credibility."

But an unwillingess on the part of successive US administrations to make public what they do know to be true about support of al Qaeda, says Riedel, leaves family members of 9/11 victims with little else but the words of a hardened former member, locked away for perpetuity in solitary confinement.

"One of the biggest mistakes of the US government since September 11 has been not putting out more information about the enemy, rather than less," said Riedel.

Riedel noted that after US Navy Seals killed Osama bin Laden in the May 2011 raid of his compound in Abbottabad, Pakistan, US officials claimed they had uncovered a trove of documents tied to al Qaeda. Only a handful were ever released. "It's been almost four years, I don't think we are going to give away any smoking guns," he said.

The content of the 28 pages, while never seen by the public, are common knowledge among many in intelligence and security circles. Revealing them, says Jones, could well cause schisms between the US and the Saudi royal family, a relationship that for more than 50 years has remained close and vital, in the view of American officials, for protecting their interests in the Middle East.

Among Moussaoui's deposition is an account of meeting Prince Salman, the half brother of then King Abdullah. Moussaoui claims he gave Salman and the other royals correspondences from Bin Laden. Last month, Abdullah died and the Saudi throne was ceded to Salman.

Jones says proving the veracity of any of Moussaoui's claims would require unveiling the pages kept secret by both President Bush and now, Obama, two years from the end of his term.

"It is time that the American people know the truth about what led to the 9/11 attacks," he added.