A quarter of a century after the September 11, 2001 attacks, the U.S. Central Intelligence Agency has declassified a body of documents recording that as far back as the late 1990s, the agency's analysts had repeatedly pointed to the possibility of attacks on U.S. soil. The released materials include scenarios involving the hijacking of civilian aircraft and their use as weapons, making this publication one of the most detailed looks at what intelligence knew — and what it failed to prevent.
What exactly the CIA declassified
The declassified materials cover the period from the presidency of Bill Clinton to the administration of George W. Bush, that is, the years preceding September 11, 2001. On that day, 19 Al-Qaeda militants carried out a series of passenger plane hijackings, killing nearly 3,000 people and prompting a fundamental overhaul of U.S. security policy. The release of the documents 25 years later makes it possible to compare early intelligence assessments with the actual course of events.
Early warnings: 1998
According to the documents, a report dated September 10, 1998 already contained a warning that Al-Qaeda "could send planes loaded with explosives to an American city." A document from December of the same year assessed the risk of attacks involving plane hijackings as rising. Thus, the idea of using aviation as a weapon was present in the intelligence landscape several years before the attacks.
Why preventive measures were not taken
The key limitation recorded in the materials is the fragmentary nature and insufficient detail of the information available at the time. The intelligence did not contain specific indications regarding timing, targets, or methods of attack, which limited the scope for operational and preventive action. It is precisely this vagueness, rather than a complete absence of warnings, that explains why the signal was not translated into concrete countermeasures.
Contradictory data
There is a discrepancy between the early formulations and the actual course of the attacks in the nature of the threat. The 1998 report spoke of "planes loaded with explosives," whereas on September 11, 2001, the hijacked airliners were used as flying bombs with fuel as the charge, without any additional explosive devices. Moreover, although warnings about the risk of hijackings existed, the released materials contain no indication that they included sufficiently specific details to trigger a preventive operation. Thus, the fact of early awareness of the threat and its practical operability are two different dimensions that do not align in the documents.
The new threat landscape according to DHS
The U.S. Department of Homeland Security (DHS) notes that the nature of the threat has shifted: if centralized organizations previously dominated, the main danger now comes from individuals and small groups that radicalize on their own. The agency also warns of risks associated with generative artificial intelligence and unmanned aerial vehicles, which may be used both for propaganda purposes and to directly support attacks.
The declassified documents do not change the outcome of September 11, but they record a systemic intelligence problem: the presence of warnings is not equivalent to the presence of actionable information. For modern security policy, this means that the focus is shifting from combating large networks to countering decentralized threats and technological risks.
