airplane going over 500 miles an hour? it's russian roulette. >> in the wake of the crash, the questions began immediately. how could this plane with its clean safety record suffer such a catastrophic failure in flight? right away there are some key clues. at the accident scene, a critical component called the fan disc is missing from the number two engine. it isn't found until three months later in a field 70 miles away in alta, iowa. that's where the plane experienced that initial violent jolt. these photos taken by a witness on the ground as united 232 was about to slam into the runway also provide investigators with critical information. >> you can see that there are holes in the horizontal stabilizer from the debris as