Did the US really know about the September 11 attacks before they happened?

Answer 1

While some people believe that there were enough clues for U.S. intelligence and security agencies to figure out that Al Qaeda was planning to stage some kind of an attack using hijacked civilian airliners, the U.S. government had no information about a specific plot or the targets before the attacks took place. So no, the U.S. gov't did not know about the attacks of 9/11/2001 before they happened.