A new study from the University of Bath sheds fresh light on critical US intelligence failures ahead of the 9/11 attacks, including new evidence that changes how the CIA’s repeated failure to share information with the FBI about two hijackers should be understood.

The study, 9/11 as a Catastrophic Systems Failure: Reassessing the Unclassified Evidence by security expert Dr Patrick Bury, raises fresh questions about how two hijackers, who crashed American Airlines Flight 77 into the Pentagon, were ultimately missed by the US intelligence system.

Drawing on recently declassified FBI and CIA records, alongside official investigations and court disclosures, it examines new evidence concerning Saudi-linked individuals who supported the men in the United States and, crucially, asks whether that environment was connected to CIA efforts to gain intelligence access to al-Qaeda.

It examines the increasingly plausible possibility that the hijackers – Khalid al-Mihdhar and Nawaf al-Hazmi – were initially viewed as potential avenues of intelligence access into al-Qaeda’s network rather than as imminent threats to the US homeland.

Dr Patrick Bury, former NATO analyst and Reader in Security at the University of Bath, says: “The evidence shows that future hijackers were known to parts of the intelligence system long before the attacks, yet critical information held by the CIA repeatedly failed to reach the people and organisations that could have acted on it. The question is why known intelligence did not generate an effective response.

“Importantly, we can now see a much denser and more strongly substantiated Saudi-linked facilitation environment around Mihdhar and Hazmi, including individuals with documented or suspected links to Saudi intelligence, than the public record available after the original inquiries could establish.”

The study – the first systematic academic reassessment to integrate this fuller public record into the wider explanation of the 9/11 intelligence failure – notes that the newly available material does not establish CIA-Saudi operational coordination or Saudi state sponsorship, but does change the evidential context in which longstanding questions about CIA non-disclosure must be assessed.

“It also raises important questions about intelligence handling, threat assessment and the interaction between known intelligence and the support networks that emerged around the men. Combined with organisational dysfunction, overload and liaison sensitivity, these factors helped sustain a pattern in which repeated opportunities for correction were lost,” Dr Bury says.

The first pattern has been known for years. As the CIA monitored an important al-Qaeda meeting in Kuala Lumpur in January 2000, it knew future hijacker al-Mihdhar held a valid US visa, but the information was not disseminated through normal intelligence reporting channels. FBI personnel assigned to the CIA’s Counterterrorist Center attempted to notify FBI headquarters, but those efforts were blocked. Later, as the FBI investigation of the USS Cole attack increasingly converged on the same network, investigators made repeated requests to the CIA for relevant intelligence, yet the full picture was still not disclosed.

The second pattern has become much clearer only as classified evidence has been made public. Recently released and declassified material shows that, after arriving in the United States, Mihdhar and Hazmi quickly became embedded within a much more substantial Saudi-linked facilitation environment than the original inquiries were able to establish.

A major part of that new evidence concerns Omar al-Bayoumi, the Saudi national who helped the men establish themselves in California. Recently declassified FBI material shows that Bayoumi had closer links to Saudi government and intelligence structures than earlier public investigations were able to establish.

“It is the relationship between those two patterns that changes the evidential picture,” Dr Bury says. “The repeated CIA non-disclosure has long been known. What we can now see much more clearly is the Saudi-linked environment that quickly developed around the same two men once they were in the United States. That does not establish why the CIA retained the intelligence, but it substantially strengthens the plausibility of operational access considerations as one part of the explanation.”

Dr Bury adds: “An increasingly plausible explanation is that CIA officers initially regarded al-Mihdhar and al-Hazmi as potential intelligence access opportunities connected to al-Qaeda’s network rather than simply as targets for immediate disruption. The new evidence strengthens that explanation, but does not, yet, establish that this was why the intelligence was retained.”