On October 31st 1999 EgyptAir Flight 990 struck the ocean with the loss of all on board. The end of the NTSB's final summary reads thusly "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."