The declassified documents, dated between 1992 and 2004, are heavily blacked out and offer little new information about what the U.S. knew about the al-Qaida plot before 2001. Many of the files are cited in the 9/11 Commission report, published in 2004.
The commission determined the failure that led to 9/11 was a lack of imagination, and U.S. intelligence agencies did not connect the dots that could have prevented the attacks.