It was the worst terrorist attack in Britain's history, the deadliest assault on U.S. civilians until 9/11 and a political powder keg that roiled governments around the world. On Dec. 21, 1988, a bomb exploded in the forward cargo hold of Pan Am Flight 103, a jetliner flying from London to New York. Within less than a minute, the Boeing 747 splintered into thousands of pieces and fell 31,000 feet, smashing down in the village of Lockerbie, Scotland. The impact killed 11 villagers and destroyed 21 homes. None of the 259 people on board the aircraft survived. On August 21,...