The co-pilot of an airliner which crashed in New York in November 2001 made a fatal error with the aircraft's rudder, US investigators have found.
The crash sparked fears of a new 9/11-type attack
Flight 587 crashed into the Queens area with the loss of 265 lives soon after take-off from Kennedy Airport, bound for the Dominican Republic.
The disaster sparked fears of another terror attack, coming soon after 9/11.
The inquiry also queried pilot training at American Airways as well as the rudder design of the Airbus involved.
First Officer Sten Molin responded to turbulence incorrectly by moving the rudder back and forth, an investigator said on Tuesday.
Within seconds, the plane's tail had snapped off and the plane was doomed, said Robert Benzon of the National Transportation Safety Board (NTSB).
Molin's response had been "unnecessary and aggressive", he said, but added that the co-pilot had been unaware that he was applying more pressure than the tail could bear.
Mr Benzon was giving details shortly before the release of the NTSB's official findings, expected later on Tuesday.
'Let's go for power'
The Airbus A300-600 is said to have fish-tailed before sliding sideways, like a car skidding on a slippery road.
It came down just one minute and 45 seconds after taking off from New York's JFK airport on 12 November.
The plane's tail snapped off under pressure from side forces
Molin was at the controls of the climbing plane when it encountered the turbulence.
Capt Edward States is recorded as urging him to "hang onto it" to which the co-pilot replies: "Let's go for power, please".
A second later a loud bang - believed to be the tail coming off - and the roar of air rushing against the plane as alarms go off can be heard.
States is last heard saying: "Get out of it! Get out of it!"
All 260 passengers and crew aboard were killed as well as five people on the ground.
American Airlines (AA) and Airbus have blamed each other for the crash, but both came under fire from the NTSB's investigator:
- AA was found to have improperly trained its pilots to use the
aircraft's rudder while recovering from upsets, and its simulator training may have exacerbated the problem
The rudder control system on the Airbus A300-600 was found to be sensitive at higher air speeds, which is potentially hazardous.
Both Airbus and AA agree that if the co-pilot had taken his foot off the rudder pedal, the tail would not have been lost and the accident would have been avoided, says the BBC's Jeremy Cooke in New York.
But the manufacturers say they issued warnings about the vulnerability of the tail section when put under heavy load.
The airline says it had no such information and that consequently, the co-pilot had no way of knowing that his actions were putting too much stress on the aircraft.