Law enforcement

9/11 hijackers lived with FBI informant

The "best chance" of preventing the 9/11 terror attacks was directly under US intelligence authorities' noses, but they had no idea just how close they came, a chilling report revealed.

In fact, two of the hijackers were even sharing a house with an FBI informant.

Not only did the FBI fail to notice suspects who were living in plain sight, authorities missed multiple warnings which could have prevented hijackers slamming planes into the World Trade Centre, the Pentagon, as well as the failed attack on the White House which crash-landed in a field in Pennsylvania.

A number of frustrating sequences of events have been unearthed to mark the 10-year anniversary of the public release of the Office of the Inspector General's (OIG) review of the FBI's handling of intelligence information related to the September 11 attacks.

These include the devastating realisation that the whole tragedy could have been avoided if a series of unfortunate events hadn't unfolded, including the fact the United States had not placed Saudi Arabia as a threat to national security.

The report details numerous missed opportunities for the FBI to learn about Khalid al-Mihdhar, Nawaf al-Hazmi and later, Hani Hanjour, who along with two others, hijacked American Airlines Flight 77 and flew it into the Pentagon.