EgyptAir Flight 990
Egyptair Flight 990 was a flight that flew on a Los Angeles-New York-Cairo route (Los Angeles International Airport in Los Angeles, California to John F. Kennedy International Airport in New York, New York to Cairo International Airport in Cairo, Egypt). On October 31, 1999, Flight 990 dived into the Atlantic Ocean near Nantucket Island, Massachusetts.
Radar and radio contact with the Boeing 767-366ER aircraft (callsign SU-GAP) was lost 30 minutes after the aircraft departed JFK Airport in New York on a flight to Cairo. The flight descended from flight level FL330 to FL191 in 36 seconds.
The flight was carrying 15 crew members and 202 passengers.
An investigation by the NTSB determined that the copilot, Gameel Al-Batouti, seized control of the plane when the pilot was out of the cockpit, turned off the autopilot, and deliberately crashed the plane into the ocean, while calmly reciting "I rely on God" and counteracting the pilot's valiant efforts to recover from the dive. The investigation and its results drew severe criticism from the Government of Egypt. The numerous alternative theories proposed by Egyptian authorites were tested by the NTSB - none were found to match the facts.
Myth
Several days after the crash, many people, particularly in the United States, started calling the tragedy a possible warning of things to come, based on the flight's number (990, which people thought was a message from God to expect tragic things during the changing, on New Year's eve, from 1999 to 2000) and the worrying Y2K situation. Soon after the new year arrived without incidents, of course, the myth of flight 990 being a sign from God disappeared.
Conspiracy Theory
Many ([1]) believe that the crash was the first successful test of a 767/757 remote control system that was used in 9-11. There were high-ranking Egyptian military officers on board ([2]) and the NTSB is not known to have investigated this possibility.