Pan Am flight 103 exploded over Lockerbie, Scotland, in December 1988, killing all 259 people on board and 11 on the ground. There were 189 Americans on the plane. Now, the only man ever convicted in the attack is a free man. Abdelbeset Ali Mohmed al Megrahi was freed from a prison in Scotland today and allowed to return to Libya because he has terminal prostate cancer, officials say.