USA Today is reporting that the FBUI knows who the twentieth hijaker was. "We are fairly confident we know who No. 20 is," said the official, who is involved in the 9/11 probe and asked not to be identified. The official said the unidentified al-Qaeda operative got into the USA but "had to leave" the country shortly before 19 hijackers carried out the attacks that killed more than 3,000 people. The official would not say why the operative left, whether he is alive or whether he is in U.S. custody.