CLOSED. Clark Air Base, a bastion of U.S. air power in the Pacific until the eruption of Mount Pinatubo put it out of business last June. In a somber ceremony General Jimmie Adams, commander of U.S. Pacific Air Forces, handed the ash-covered installation over to the Philippine government, which had granted the U.S. use of the facilities since 1947. Located near Manila, Clark played a key logistical role during the Vietnam War but lost its strategic value with the end of the cold war.