CIA declassified 71 presidential briefings warning Clinton and Bush of al Qaeda attacks.
The release includes 70 reports from before the attacks and one document from September 12.
The reports warned Bill Clinton and George Bush of plane hijackings, but had no set dates or targets.
Key warnings in the briefings:
- September 1998: Briefings warned al Qaeda might fly a bomb-packed plane into a US city.
- December 1998: Briefings said two bin Laden men slipped past airport checks in a New York test run.