On July 17, 1996, at 8:31 pm/et, TWA Flight 800 exploded midair and fell into the Atlantic. All 230 onboard perished. Federal investigators meticulously reconstructed the aircraft, looking for any evidence of terrorism and found none. They concluded thata malfunction in the center fuel tank caused the explosion. But this official conclusion has never satisfied a coterie of independent investigators and conspiracy theorists. We weigh existing evidence against various theories to let you decide.