This interactive timline lets you review the 9/11 Commission's findings on events and intelligence available before the 9/11 attacks — sources include the relevant documents, contemporary news coverage and new reports.
In April 2004 the 9/11 Commission concluded the terrorists had 'exploited deep institutional failings within our government.' In August 2007 the inspector general of the CIA released a summary of an internal secret report that comes down hard on the agency and its officers for not discharging their responsibilities 'in a satisfactory manner.' For example, the report says that 50 to 60 officials had intelligence that two of the hijackers may have been in the country, but no one thought to notify the FBI.
Simply click on a name or the document symbol next to an event to find out what the intelligence community and executive branch knew — and when they knew it.