NTSB investigation and conclusion[edit]
The NTSB's investigation fairly quickly centered on the actions of the Relief First Officer, Gameel Al-Batouti, and this drew relatively minor criticism from Egyptians.[17] The NTSB determined that the only way for the observed split elevator condition to occur was if the left seat pilot (the Captain's position) was commanding nose up while the right seat pilot (the First Officer's position) commanded nose down. As the Egyptian investigation forwarded various mechanical failure scenarios, they were each tested by the NTSB and found not to match the factual evidence. The NTSB concluded that no mechanical failure scenario either they or the Egyptians could come up with matched the evidence on the ground, and that even if mechanical failure had been experienced, the 767's design made the situation recoverable.[1]
The NTSB's final report was issued on 21 March 2002, after a two-year investigation, and concluded as follows:[1]
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.