The maintenance log reported problems with the pitch trim, which helps keep the nose in an up or down position, and the yaw damper, which uses the rudder to keep an airplane from swaying.
The problem was corrected when a mechanic reset the computers that control the components, according to the log.
Aviation consultant Jim McKenna said safety investigators will focus on those components of the Airbus A300-600. "They'll take a very close look at it," McKenna said.
"This is drawn from things that we handed over to them, so it's something we knew about," American Airlines spokesman Tim Kincaid said. "We're cooperating fully with the investigation."
The NTSB said that the vertical stabilizer or tail fin and the attached rudder fell off the plane, as did both engines. The Nov. 12 crash killed all 260 people on board and five on the ground.
Following the accident, the Federal Aviation Administration ordered inspections of the tail, which is made from lighter-weight, nonmetallic composites.
The NTSB is conducting ultrasound and other inspections of the vertical stabilizer and rudder, and is developing a plan for additional tests of the composites.
Maintenance records showed that the vertical stabilizer and rudder last were inspected visually in December 1999, and no problems were reported, the NTSB said.
Board investigators reported that they found no evidence that the engines broke apart, sending shrapnel into nearby control systems, nor any evidence of a collision with a bird. There also was no evidence that there was a fire or a malfunction.
NTSB investigators again reported that they have found no evidence of a terrorist attack. All the evidence continues to indicate that the crash of Flight 587 was an accident, the board said.
By Jonathan D. Salant
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