 Can the lessons of one air disaster help prevent another? What caused Swissair Flight 111 to plunge into waters off the coast of Nova Scotia on September 2, 1998, killing all 229 people aboard? After four years and almost $40 million, investigators revealed that the accident was caused by factors that, alarmingly, still exist on many planes today. NOVA was given unprecedented access to this intricate investigation, involving a seemingly hopeless search for evidence among two million pieces of debris scattered across the ocean floor. The recovery of the flight data recorder and cockpit voice recorder raised hopes until both were found to have failed during the last six minutes of the flight. Despite these daunting challenges, crash detectives methodically collected, sifted, and sorted through the wreckage to reassemble a large portion of the plane in a giant hangar, building a detailed picture of Flight 111 s last moments. After years of painstaking recovery, reconstruction, and testing, the investigators submitted their conclusions and recommended new safety measures. But some experts still believe that another disaster like this one could be just a matter of time.