A briefer wrote to then-President Clinton that bin Laden’s ‘preferred option is to strike the US on its own soil in Washington’, and that al-Qaeda ‘may fly an explosive-packed airplane into a US city’.

Several dozen presidential briefing documents declassified on the 25th anniversary of the September 11, 2001, attacks detail intelligence government officials had gathered about Osama bin Laden and al-Qaeda leading up to the hijackings that killed nearly 3,000 people and upended the United States’ national security.

The documents illustrate security analysts’ tracking of bin Laden’s movements and support system, as well as concerns about possible threats to US targets. They also detail officials’ understanding of his network in the US and other countries, including how his operations were financed.

Proclaiming it “an act of exceptional transparency”, CIA Director John Ratcliffe said the documents were the agency’s single largest release of declassified presidential daily briefs — the highly classified briefings prepared by the nation’s intelligence community for the government’s most senior leaders.

The documents range from a February 1998 file, prepared for then-President Bill Clinton, titled “Terrorists Seeking WMD Capability” and mentioning bin Laden and other Islamic extremists, to a September 12, 2001, report in which a source indicated the attacks had been planned for two years and had also targeted the US Capitol.

An April 1998 document described the Taliban’s unwillingness to hand over bin Laden, at the time seen as their “guest” in Afghanistan, noting their “gratitude for his assistance during the Soviet occupation” was making them “reluctant to alienate him by monitoring or controlling his activities”.

Five months later, a briefer wrote that bin Laden’s “preferred option is to strike the US on its own soil in Washington” and that al-Qaeda “may fly an explosive-packed airplane into a US city”.

Potential hijackings were also discussed in December 1998, when a briefer described how conspirators “have evaded security checks during a recent trial run at an unidentified New York airport”, and “some members of the Bin Ladin network have received hijack training”.

Other documents detail bin Laden’s pursuit of materials for making “dirty bombs”, conventional weapons infused with radioactive material. By June 1999, according to intelligence officials, his operatives had conducted such experiments with explosives to “increase their energy output”.

Many of the documents were redacted to conceal sources’ names and other identifying information. They didn’t appear to break any new ground on the planning of the attacks or on US officials’ understanding of how they had unfolded.