This episode's headline: News Summary; Colombia: Details of Disaster; Road to the Summit: Arms Control; Speaker's View; Aaron Copeland: Master of Music. The guests include In Washington: MARINO PEREZ MURCIA, Colombian RadiofiTV; On Capitol Hill: Rep. THOMAS P. O'NEILL, Speaker of the House; Reports from NewsHour Correspondents: JIM LEHRER, in Washington. Byline: In New York: ROBERT MacNEIL, Executive Editor; In Washington: JUDY WOODRUFF, Correspondent