EgyptAir Flight 990 (MS990/MSR990) was a regularly scheduled flight from Los Angeles International Airport to Cairo International Airport, with a stop at John F. Kennedy International Airport, New York City. On October 31, 1999, the Boeing 767-300ER operating the route crashed into the Atlantic Ocean about 60 miles (100 km) south of Nantucket Island, Massachusetts, killing all 217 passengers and crew on board.

Since the crash occurred in international waters, it was investigated by the Ministry of Civil Aviation's Egyptian Civil Aviation Agency (ECAA) and the National Transportation Safety Board (NTSB) under International Civil Aviation Organization rules. As the ECAA lacked the resources of the NTSB, the Egyptian government asked the American government to have the NTSB handle the investigation. Two weeks after the crash, the NTSB proposed handing the investigation over to the Federal Bureau of Investigation, as the evidence they had collected suggested that a criminal act had taken place, and that the crash was intentional rather than accidental. The Egyptian authorities refused to accept the proposal to hand the investigation over to the FBI, so the NTSB was forced to continued the investigation alone, despite it falling outside of their investigative purview.

The NTSB found that the probable cause of the accident was 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", but did not determine a specific reason for the relief first officer's alleged actions. The ECAA concluded that the incident was caused by mechanical failure of the aircraft's elevator control system. The report suggested several possibilities for the cause of the accident, focusing on the possible failure of one of the right elevator's power control units. However, the NTSB dismissed the ECAA report after it was found that no scenario could explain the doomed flight's final movements other than an intentional human act.