"The crash of TWA [Trans World Airlines] Flight 800, potentially one of the most lethal international terrorist acts ever perpetrated against the United States, touched off the most extensive, complex, and costly air disaster investigation in US history. Had it been the result of state-sponsored terrorism, it would have been considered an act of war. FBI and National Transportation Safety Board (NTSB) investigators almost immediately focused on three possible causes: a bomb, a missile, or a mechanical failure. The missile theory seemed particularly plausible because of reports from dozens of eyewitnesses in the Long Island area who, on the evening of 17 July, recalled seeing something resembling a flare or firework ascend and culminate in an explosion."
Central Intelligence Agency: https://www.cia.gov/