The immediate human toll of this 1994 disaster was staggering: all 132 people aboard died on a Pennsylvania hillside. The subsequent investigation was a maze of politics, bizarre theories, and shrouded answers. Bill Adair, an award-winning journalist, was granted special access to the five-year inquiry by the National Transportation Safety Board (NTSB) while its investigators tried to determine if the world's most widely used commercial jet, the Boeing 737, was really safe.