A plane travelling from Paris to Cairo with 66 people on board has crashed, Egyptian officials said.
EgyptAir flight MS804 disappeared from radar 10 miles inside Egyptian air space over the Mediterranean at 2.30am Cairo time (1.30am BST) after taking off just under three and a half hours earlier from Charles de Gaulle Airport.
A major search and rescue operation has been launched by Egyptian and Greek authorities to find the remains of the aircraft, with reports of a flash in the sky over the Mediterranean.
EgyptAir said the 56 passengers included 30 Egyptians, 15 French, two Iraqis, and one each from Britain, Sudan, Chad, Portugal, Algeria, Canada, Belgium, Kuwait and Saudi Arabia.
The Foreign Office said it could not confirm that a Briton was on board.
A spokeswoman said: "Following reports that EgyptAir flight MS804 has gone missing en route from Paris to Cairo, we are in urgent contact with the authorities in Paris and Cairo to obtain further information."
The French government said President Francois Hollande spoke with Egyptian President Abdel-Fattah el-Sissi by telephone, and they agreed to "closely co-operate to establish the circumstances" in which the flight disappeared.
The written statement cited Hollande as saying he shares the anxiety of families.
Flight MS804 left Charles De Gaulle Airport at 11.09pm Central European Summer Time (10.09pm BST).
The airline initially said said there were 59 passengers on board but later said there were 56, including one child and two babies.
Three EgyptAir security personnel were also on board as well as seven cabin crew members.
Ahram, Egypt's state-run newspaper, quoted an airport official saying that the pilot had not sent a distress signal before it disappeared. The last contact with the plane was 10 minutes before it vanished, he was quoted as saying.
But EgyptAir tweeted in Arabic later that Egypt's armed forces had received a distress signal "from the plane's emergency devices".
The airline confirmed that it was flying over the Mediterranean Sea about 170 miles from the Egyptian coast when it disappeared.
It said it was hosting passengers' families near Cairo Airport and was providing doctors and translators.
The airline originally tweeted that the plane lost contact with radar at 2.45am Cairo time but later confirmed that it lost contact at 2.30am and was due to land at 3.15am.
In October last year, 224 people were killed when a Russian aircraft crashed over Egypt's Sinai Peninsula minutes after it took off from the Red Sea resort of Sharm el-Sheikh.
EgyptAir has provided free contact numbers for families concerned for relatives. From outside Egypt, anyone concerned should call + 202 2598 9320.
Greek authorities have deployed two aircraft, a C-130 military plane and one early warning aircraft, the Hellenic National Defence General Staff said.
It also said a frigate was heading to the area and helicopters were on standby on the southern island of Karpathos for potential rescue or recovery operations.
Ahmed Adel, vice chairman of EgyptAir's parent company, told CNN the plane had "no snags" arriving in Paris or when it departed for Cairo.
He said there was no special cargo on the flight and no notification to the captain of any dangerous goods.
He added: "We did not confirm if there was a distress call. It just lost contact and we lost it on the radar of the air traffic controllers."
An emergency response room has been set up at the Integrated Operations Control Centre at Cairo Airport.