President Reagan offered condolences Friday to families of the victims of the Pan Am crash in Scotland but said to issue a public warning based on an anonymous threat would "literally have closed down all air traffic in the world." He said it would be impossible to issue public warnings about each supposed threat. Reagan spoke to reporters outside the White House as he departed for a two-week California vacation. "A tragedy that steals the hopes and dreams from our society magnifies the loss," Reagan said. "I know that America and the world mourn the loss of these wonderful people, and I ask that all our citizens say a special prayer this Christmas for those who have felt the pain of those losses," the president said. "May God be with you."