According to Thomas Kean, chair of the 9/11 Commission, "Sixteen of the nineteen shouldn't have gotten into the United States in any way at all because there was something wrong with their visas, something wrong with their passports.
Khalid al Mihdhar and Nawaf al Hazmi had both been identified as al-Qaeda agents by the CIA, but that information was not shared with the FBI or U.S. Immigration, so both men were able to legally enter the U.S. to prepare for the 9/11 attacks [REF].