Newly released data on the crash of American Airlines Flight 587 raises the possibility that the crew, responding to turbulence, hit the rudder control unusually hard, creating stress on the tail fin that may have contributed to its cracking off.
But nothing released so far would rule out a malfunction that caused the rudder to move on its own, or that the vertical tail section somehow was already weakened and cracked off under far less stress than it could normally handle.
Information from the flight data recorder showed that after the aircraft twice hit wake turbulence from a Boeing 747, the rudder jerked the Airbus A300-600 sharply right twice, then left. It then began turning sharply left and diving, probably when the vertical tail fin broke off and the plane went out of control.
The US National Transportation Safety Board would offer no interpretation of the raw data, and many months of analysis lie ahead before the board and its staff can determine the probable cause of Monday's disaster. But it already appears that this crash will not be traced to one single cause, and will prove instead to be the result of a chain of unlikely events.
The board has not fully ruled out terrorism or other criminal activities, but data gathered with each passing day seem to make such possibilities increasingly remote. "The investigation continues to point to an accident," said NTSB chair, Ms Marion Blakey.
When the Airbus A300's tail fin came off, the plane became uncontrollable. It gyrated wildly, apparently producing enough force to crack off the top of the pylons that attach the two engines to the wings. The aircraft then spiralled into a residential neighbourhood in New York, killing 265 people.
Many issues must be addressed by investigators, including the condition of the six attachments that held the tail fin to the fuselage until they ripped apart. These attachments were made of a modern composite material called carbon fibre-reinforced plastic.
The French civil aviation authority called yesterday for inspections of all Airbus A300 passenger jets in service in France.