This episode's headline: Downed Airliner; One Nation Indivisible. The guests include MOHAMMAD JA-AFAR MAHALLATI, Iranian Ambassador To The U.N.; STANSFIELD TURNER, Former C.I.A. Director; HARLAN ULLMAN, Center For Strategic Studies; HOWARD TEICHER, Former NSC Official; JAMES BILL, College of William & Mary; ESSAYIST: ROGER ROSENBLATT. Byline: In Washington: JAMES LEHRER; In New York: CHARLAYNE HUNTER- GAULT