It remains unclear whether the disappearance was due to technical failure or any other reason. Egyptian Prime Minister Sherif Ismail said it is too early to rule out any explanation for the incident, including terrorism.
 
Egypt Air said the plane sent an emergency signal -possibly from an emergency beacon attached to the plane- at 04:26 a.m., two hours after it disappeared from radar screens. The crew never sent an emergency signal or reported any issues during their last communication with Greek authorities when passing through Greek airspace. In water crashes, an underwater locator beacon attached to the aircraft's flight recorders starts to emit a signal or ping. This helps the search and rescue teams to locate the boxes, and the location of the crash. Therefore, the airline believes the plane crashed into the sea.
 
The aircraft was carrying 56 passengers, including one child and two infants, and 10 crew, EgyptAir said. They included 30 Egyptian, 15 French nationals, 2 Iraqis and one national from each of the following countries: Britain, Canada, Belgium, Portugal, Algeria, Sudan, Chad, Saudi Arabia, Kuwait.
 
Asked if he could rule out that terrorists were behind the incident, Prime Minister Ismail said: “We cannot exclude anything at this time or confirm anything. All the search operations must be concluded so we can know the cause. Search operations are ongoing at this time for the airplane in the area where it is believed to have lost contact” he told reporters at Cairo airport.
 
Greek authorities have been assisting with the search, deploying aircraft and a frigate to sea. According to Reuters, a Greek defense ministry source said authorities were also investigating an account from the captain of a merchant ship who reported a “flame in the sky” about 130 nautical miles south of the island of Karpathos. So far no debris has been found.
 
“The pilot did not mention any problems” Kostas Litzerakis, the head of Greece's civil aviation department, told Reuters. However, during the transfer to Cairo airspace, Greek controllers were unable to reach the pilot and the plane vanished from their radars shortly after leaving Greek airspace, he added.
French President Francois Hollande's office said the French leader had just spoken to his Egyptian counterpart and that both sides would cooperate closely. Egypt and France exchanges condolences over the vanished EgyptAir plane.
 
“We are in close contact with the Egyptian authorities, both civil and military” French Prime Minister Manuel Valls told French radio. “At this stage, no theory can be ruled out regarding the causes of the disappearance”.