EgyptAir flight MS804 disappeared from radar over the Mediterranean Sea on Thursday (May 19) in a crash that Egypt said may have been caused by a terrorist attack.
The Airbus A320, with 56 passengers and 10 crew members, left Charles de Gaulle airport in Paris for Cairo International Airport on Wednesday (May 18) at 11.09pm Paris time. Flying in clear skies, the plane was 10 miles into Egyptian airspace - or three and a half hours after takeoff - when it disappeared from radar at around 2.30am Egypt time
Here's what we know so far:
What do we know about the plane?
The Airbus A320 was built in 2003 and had clocked 48,000 flight hours. It had passed through airports in Tunisia and Eritrea in the four journeys it made on Wednesday before the Paris-Cairo flight.
Who was on board the flight?
The passengers' nationalities have been disclosed as: 15 French, 30 Egyptian, 1 British, 1 Belgium, 2 Iraqis, 1 Kuwaiti, 1 Saudi, 1 Sudanese, 1 Chadian, 1 Portuguese, 1 Algerian, 1 Canadian. The airline said two babies and one child were on board.
There were also 10 crew members on board. The pilots were Mahamed Saeed Ali Shouqair and Mohamed Mamdouh Ahmed Assem. Shouqair had 15 years’ experience and was in charge of training and mentoring younger pilots. A Facebook page that appeared to be Shouqair’s showed no signs of Islamist sympathies. He has been with EgyptAir since 2004 and lives in Cairo.
What happened before the plane disappeared?
France’s aviation safety agency said the plane had transmitted automatic messages indicating smoke in the cabin. The messages were transmitted through the Aircraft Communications Addressing and Reporting System (Acars), a digital system that transmits short messages between aircraft and ground stations.
The disclosure by a spokesman for France’s Bureau of Investigations and Analysis came after a respected aviation journal, Avherald, published details about the last minutes on the plane based on the Acars transmissions. The data is written tersely in abbreviations and codes.
They revealed a rapid loss of control, with alarms and computer-system failures just before the plane was lost from radar.
1.48am (Cairo time): The Hellenic Civil Aviation Authority said the flight was proceeding normally when Greek traffic controllers last spoke with the pilot of Flight MS804, who seemed in good spirits.
2.26am: An Acars message indicated that the plane’s right cockpit window had been opened. This could have been done to vent smoke, according to Mr Robert Mann, a former airline executive and an industry analyst, or something else could have caused the breach.
Between 2.26am and 2.28am: There were two smoke indications, one in a bathroom and another in the avionics bay, the part of the plane where much of its electronic equipment is housed. Mr Mann cautioned that these messages did not necessarily mean there was a fire.
The messages could also have been prompted by rapid decompression of the aircraft, which can produce condensation that the plane’s sensors could mistake for smoke.
2.29am: There were two more alerts having to do with the plane’s flight control computer systems. First, there was a problem with the autoflight control computer. The jet would have been flying near its maximum speed and elevation at that time. That is the most efficient way for jetliners to fly, and it is safe, Mr Mann said, but pilots prefer to rely on autopilot systems in those conditions because if they were ever to lose control of the plane, it could be hard to regain. That is why pilots sometimes call those conditions the “coffin corner”.
Greek authorities said the plane fell 22,000ft and "swerved sharply" in Egyptian airspace. "The plane carried out a 90-degree turn to the left and a 360-degree turn to the right, falling from 37,000ft to 15,000ft and the signal was lost at around 10,000ft," Defence Minister Panos Kammenos said.
What could have caused the crash?
So far no cause has been established. Here are some theories put forward and their likelihood:
Both France and Egypt have been leading targets for Islamist extremists in recent months. Last October, the Islamic State in Iraq and Syria (ISIS) militant group claimed responsibility for bombing an A-321 plane - belonging to Russian charter firm Metrojet - that crashed into the Sinai desert on its way from the Egyptian resort of Sharm el-Sheikh to St Petersburg in Russia, killing 224 passengers and crew.
One major factor pointing to a terror attack on EgyptAir Flight MS804 is the fact that there does not appear to be any distress signal sent from the plane. "A technical problem, a fire or a motor malfunction doesn't cause an instantaneous accident and the crew has time to react," said Mr Jean-Paul Troadec, former president of the French air accident investigation bureau. "Here, the crew didn't say anything," he added.
A Greek Defence Ministry source was quoted as saying that the authorities were investigating reports from the captain of a merchant ship of "a flame in the sky" around 130 nautical miles south of the Greek island of Karpathos, near where the last contact with the plane was made.
If a bombing is established, the question for investigators will be how a device was smuggled aboard a flight taking off from France's busiest airport, Charles de Gaulle.
2. Mechanical failure
Experts said the chances of a mechanical malfunction were slim. The aircraft passed through airports in Tunisia and Eritrea in the four journeys it made on Wednesday before the Paris-Cairo flight, but no warning flags were raised.
In addition, the A-320 has an excellent safety record as the best- selling, medium-range airliner in the world. An A-320 takes off or lands every 30 seconds around the world, according to aeronautics expert Gerard Feldzer.
EgyptAir vice-chairman Ahmed Abdel said there were "no reported snags" from the crew in Cairo or Paris, nor was there any special cargo or notification of dangerous goods on board.
3. Shot down
The plane which was flying at 11,000m, first swerved 90 degrees to the left, then spun through 360 degrees to the right, before plunging and vanishing from Greek radar screens.
Experts noted that a jet flying at 11,000m would be out of reach of portable rocket launchers used by militant groups in the Middle East. "We cannot exclude the possibility it was shot down by another aircraft by mistake, but it is likely we would already know," said Mr Feldzer.
The region around northern Egypt, including the Israeli and Gazan coastlines, is "one of the most monitored regions in the world, including by satellite", he said. "It would be very difficult to hide this kind of information."
4. Rogue pilot
So far there has been no evidence to show that a rogue pilot could be the cause of the crash of flight MS804. EgyptAir said the flight crew were experienced, with the pilot clocking 6,275 hours of flying experience, including 2,101 hours on the A-320, and the first officer clocking 2,766 hours.
NEW YORK TIMES, REUTERS, AGENCE FRANCE-PRESSE, TELEGRAPH