When a flight ends in disaster, investigators must determine what, and sometimes who, caused the accident. Some cases are easy to solve, but others require unrelenting diligence and Sherlock Holmes-level powers of deduction. See what it took to solve three plane crashes that stumped examiners, one in the Florida Everglades, another in the small Scottish village of Lockerbie, and a miracle emergency landing at London's Heathrow Airport.