Chairman of the National Commission on Terrorists Attacks Upon the United States (9-11 Commission) Gov. Thomas Kean looks on at the beginning of their final two-day hearing at the National Transportation Security Board conference center in Washington, June 16, 2004. Al Qaeda has changed drastically since the Sept. 11 attacks but it will keep trying to strike in the United States to inflict mass casualties, the panel investigating the 2001 hijackings said on Wednesday. (Larry Downing/Reuters)