A written statement, declassified Thursday, from CIA Director George J. Tenet provides new insight into al-Qaida's preparations for Sept. 11 attacks. Some of its conclusions: - In 1996, Osama bin Laden's second-in-command, Mohammed Atef, studied the feasibility of hijacking U.S. planes and destroying them in flight. Tenet suggested he may have been inspired by the 1995 plot to crash a plane into CIA headquarters. The CIA only learned this after Sept. 11. Atef was killed in a U.S. airstrike last November. - A top al-Qaida operative, known as Mukthar or Khalid Shaikh Mohammed, has been linked to planning both the...