This is from the NTSB's investigation of Egypt Air Flight 990. It looks as if the plane was deliberately downed by the actions of the First Officer. the whole report is here:
1.The accident airplane's nose-down movements did not result from a failure in the elevator control system or any other airplane failure.
There was no evidence of any failure condition within the elevator system of the accident airplane that would have caused or contributed to the initial pitchover or prevented a successful recovery.
No mechanical failure scenario resulted in airplane movements that matched the flight data recorder data from the accident airplane.
Even assuming that one of the four examined failure scenarios that the investigation evaluated in depth had occurred, the accident airplane would still have been recoverable because of the
capabilities of the Boeing 767's redundant elevator system.
2.The accident airplane's movements during the initial part of the accident sequence were the result of the relief first officer's manipulation of the controls.
At the relief first officer's suggestion, a transfer of control at the first officer's position occurred earlier than normal during the accident flight.
The relief first officer was alone in the cockpit when he manually disconnected the autopilot and moved the throttle levers from cruise to idle; there was no evidence of any airplane system
malfunction, conflicting air traffic, or other event that would have prompted these actions.
The nature and degree of the subsequent nose-down elevator movements were not consistent with those that might have resulted from a mechanical failure but could be explained by pilot input.
There was no apparent reason for the relief first officer's nose-down elevator inputs.
The relief first officer's calm repetition of the phrase "I rely on God," beginning about 74 seconds before the airplane's dive began and continuing until just after the captain returned to the cockpit
(about 14 seconds into the dive), without any call for help or other audible reaction of surprise or alarm from the relief first officer after the sudden dive is not consistent with the reaction that would
be expected from a pilot who is encountering an unexpected or uncommanded flight condition.
The absence of any attempt by the relief first officer to recover from the accident airplane's sudden dive is also inconsistent with his having encountered an unexpected or uncommanded flight
The relief first officer's failure to respond to the command captain's questions ("What's happening? What's happening?") upon the captain's return to the cockpit is also inconsistent with the
reaction that would be expected from a pilot who is encountering an uncommanded or undesired flight condition.
3.The accident airplane's movements after the command captain returned to the cockpit were the result of both pilots' inputs, including opposing elevator inputs where the relief first officer continued
to command nose-down and the captain commanded nose-up elevator movements.
Nose-up elevator movements began only after the captain returned to the cockpit.
Testing showed that recovery of the airplane was possible but not accomplished.
Seconds after the nose-up elevator movements began, the elevator surfaces began moving in different directions, with the captain's control column commanding nose-up movement and the relief
first officer's control column commanding nose-down movement.
After the elevator split began, the relief first officer shut down the engines.
The captain repeatedly asked the relief first officer to "pull with me," but the relief first officer continued to command nose-down elevator movement.
The captain's actions were consistent with an attempt to recover the accident airplane and the relief first officer's were not.
The National Transportation Safety Board determines that the probable cause of the EgyptAir flight 990 accident is the airplane's departure from normal cruise flight and subsequent impact with the Atlantic Ocean as a result of the relief first officer's flight control inputs. The reason for the relief first officer's actions was not determined.<hr></blockquote>