Two weeks after the aircraft plunged into the Atlantic, the evidence about what happened is more confusing than ever, and there are multiple theories that blame everyone from Iraqi agents to a suicidal member of the flight crew.
The latest information from the aircraft's flight data recorder, released on Friday night, shows that the engines were shut down manually, an action that seems to defy logic. The crew shut them off as the aircraft fell at 0.86 Mach, a dive so steep that everything in the plane would have become weightless. And one of the last things that the crew did was to move the aircraft's elevators, the control tabs, in opposite directions.
As the plane fell, its master warning activated - a signal of some problem so severe that if not attended to immediately, the aircraft would crash. This could have been triggered by the aircraft's speed, a loss of pressure, a fire, or the unintentional disengagement of the auto-pilot.
The voice recorder might help explain what happened, but the two underwater robots searching the seas off the New England coast have found nothing. "We cannot at this time explain the circumstances that were occurring on Flight 990 that resulted in the flight profile,'' said National Transportation Safety Board Chairman James Hall.
The Federal Bureau of Investigation continues to examine the incident to see if criminal activity was involved. One line of inquiry was the mental stability of the co-pilot, agencies reported, with some US newspapers speculating that there may have been a struggle in the cockpit, or even that the crash was suicide. "There was something funny going on in that cockpit," Barry Schiff, a former TWA captain and air crash consultant, told the Los Angeles Times.