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At the Friday news briefing, James Kallstrom, head of the FBI team investigating the crash, said, "We need forensic evidence" before deciding the crash was a criminal act, at which point the FBI would take control of the case from the NTSB. By itself, Kallstrom suggested, the voice-recorder tape could not rule out the possibility of a "catastrophic" malfunction aboard TWA Flight 800, no matter how improbable most aviation experts deem that explanation to be. But the reasons for doubting the catastrophic hypothesis--and for suspecting a bomb--can be summarized as follows:
--Speed. There was an instantaneous and simultaneous loss of data flowing into the flight-data recorder and into all four microphones feeding into the cockpit-voice recorder. Communications with the ground abruptly halted, and no Mayday calls were detected. The cockpit-voice recorder contains neither alarmed comments among the crew nor beeping by warning indicators. Investigators tell Time that medical examinations of the recovered bodies of flight attendants indicate they were not strapped in their seats, anticipating trouble, but were moving about the cabin, apparently preparing to serve passengers. All these signs suggest a sudden, cataclysmic event, not a more slowly evolving mechanical malfunction.
--Spread. The wide pattern of the wreckage on the ocean floor seems to show the plane did not tumble into the water as a single entity but exploded high in the sky, well before impact. Radar records released by investigators late last week suggest the airliner flew on for 24 seconds after it was suddenly stricken, descending from 13,700 ft. to break up in a fireball at 8,500.
--Sightings. Eyewitnesses saw a fiery, midair explosion, not a plane faltering downward and nosing into the sea.
--Safety record. The Boeing 747 that was TWA Flight 800 had been flying for a quarter of a century without incident. The entire 747 fleet has been a bulwark of rugged dependability, with one anomalous exception. On May 9, 1976, a Continental Airlines Boeing 747-100, the same model as TWA Flight 800, leased by the prerevolutionary Iranian air force, exploded in flight and crashed near Madrid, killing 17 crew members. U.S. authorities who investigated the crash never came up with a certain cause of the disaster. But a commonly held hypothesis blamed a possible fuel leak, in one of the wing sections above the engines, that might have mixed with air and created a pocket of explosive gas.
All these details, however persuasive, remain speculative. Searching for tangible facts is harder than deducing from the past. Gathering forensic evidence involves, first of all, the laborious hauling up from the ocean floor of as much of the broken plane as possible. That process took a forward step last Friday when the NTSB's Francis announced that two of TWA Flight 800's four Pratt & Whitney turbo-fan engines had been located by sonar. "Obviously, engines--when you're looking at an airplane accident--are extraordinarily important," Francis said. Divers and remote-controlled cameras studied the engines and found nothing that would indicate a malfunction.