Omar al-Bayoumi, who has long denied being an extremist or a Saudi spy, is seen in one clip embracing Anwar al-Awlaki, who would later lead al-Qaeda in the Arabian Peninsula. In another, Bayoumi and Awlaki are paintballing near San Diego with an official from Saudi Arabia's Ministry of Islamic Affairs. The videos, never shown publicly before, were found among Bayoumi's possessions after his arrest in the UK by the Metropolitan Police days after the 2001 attacks.

Also found was a diagram of a plane with a flight descent equation written alongside. The BBC reports that multiple FBI agents received copies of the diagram, but it was never shared with British interrogators even though it had been couriered to the police station where Bayoumi was being held. The diagram was also kept from some FBI agents investigating Bayoumi, as well as from the 9/11 Commission. Bayoumi was never prosecuted.

The footage and documents form part of the 9/11 families' lawsuit against Saudi Arabia, which argues the kingdom was complicit in the attacks. Bayoumi is accused of aiding two of the 19 hijackers. A judge allowed the lawsuit to proceed in 2018, and thousands of documents have since been released to the court and declassified under an executive order by former President Joe Biden.

BBC Panorama and Radio 4 examined the released materials and spoke to dozens of special agents and investigators. The investigation found that the plane diagram was sent to the FBI's New York office and analysed, according to an FBI source. But a US Department of Justice official told the BBC he was never shown a proposal to prosecute Bayoumi based on the evidence, adding: "We've convicted people for less."

FBI agents in San Diego repeatedly requested copies of evidence but never received most of it. The San Diego and Los Angeles FBI offices were both blocked from interviewing Bayoumi's Saudi government contacts. Staff on the 9/11 Commission objected to the conclusion that Bayoumi was "unlikely" to have been involved with extremists, prompting the report to attribute this to "our investigators who have dealt directly with him."

Neither Bayoumi nor the Saudi government responded to the BBC's requests for comment, but both have always denied any involvement in or prior knowledge of the attacks. The FBI declined to comment.