An EgyptAir plane with 66 people on board from Paris to Cairo disappeared from radar early Thursday.
Reports say the plane, an Airbus 320, probably crashed into the sea.
An Egyptian military spokesman said a joint rescue team has been deployed to search for the flight.
The ill-fated EgyptAir MS804, an Airbus 320, was carrying 56 passengers — 30 Egyptians, 15 French and 11 from other nationalities, plus three security staffers and seven crew members.
According to the official source in the Egyptian airlines, the plane, which was on its way from Paris to Cairo, lost contact with radar at 2:45 a.m. Cairo time Thursday at an altitude of 11,280 meters and 16 kilometers inside Egyptian airspace.
The airlines said the aircraft commander has accumulated 6,275 flying hours, including 2,101 hours on the same plane model, and the co-pilot has 2,766 flying hours.
The plane, which was made in 2003, left Paris at 11:09 p.m. local time on Wednesday night for a scheduled three-hour-45-minute journey.
French President Francois Hollande and his Egyptian counterpart, Abdel-Fattah al-Sisi, vowed on Thursday to “work closely to establish as soon as possible the circumstances of the disappearance” of Egyptair MS804.