CAIRO — Egypt and Greece mounted a marine search-and-rescue operation early Thursday for an EgyptAir passenger jet with 66 people on board that disappeared over the Mediterranean shortly before it was due to land in Cairo, the airline and government officials said.
Flight 804, which departed Paris just after 11 p.m. on Wednesday, disappeared at 2:45 a.m. Cairo time, shortly after it entered Egyptian airspace, EgyptAir said on its Twitter account. The plane had been traveling at an altitude of 37,000 feet and was carrying 56 passengers, including three children.
The Egyptian military said that it had deployed aircraft and naval vessels to search for the plane in cooperation with Greece. “We are looking everywhere on land and at sea,” said Mohamed Samir, a military spokesman.
Greece said it had sent two aircraft — a C-130 and an early-warning aircraft — to the area.
There was no immediate indication of what had happened to the plane. Aviation security in Egypt has been under intense scrutiny since a bomb brought down a Russian airliner over the Sinai Peninsula in October, killing all 224 people on board.
A list of the passengers’ nationalities released by Egypt said that 30 were Egyptian, 15 were from France and the remainder were from at least eight other countries, including Algeria, Belgium, Britain and several Persian Gulf nations.
In addition to the passengers, the airline said, three EgyptAir security personnel and seven crew members were on board.
Ehab Mohy el-Deen, the head of Egypt’s air navigation authority, said that the pilot did not make a distress call before the plane vanished.
A spokesman for the civil aviation ministry, however, said the Egyptian military received a distress signal from the plane at 4:26 a.m., about two hours after EgyptAir said it had last made contact with the plane. Separately, EgyptAir wrote on its Twitter account that the military had received the distress signal from the airplane’s emergency devices.
At the airport in Cairo, relatives and friends waiting for the passengers were shepherded into a separate area, many of them red-faced and crying. Aviation security officials banned journalists from filming and interviewing people, saying they were acting on orders from the Interior Ministry, which controls the police.
In a flurry of posts on Twitter on Thursday, EgyptAir emphasized the experience of the crew of the missing airliner, an Airbus A320. The pilot has more than 6,000 flying hours, and the co-pilot has 2,700 hours, the airline said.
The office of President François Hollande of France said in a statement on Thursday morning that Mr. Hollande had spoken over the phone with the Egyptian president, Abdel Fattah el-Sisi, about the flight, and that the two countries would cooperate.
Speaking on the French radio station RTL, Prime Minister Manuel Valls said that the French authorities were still gathering information about the disappearance and that, “at this stage, no hypotheses on the causes of this disappearance can be ruled out.”.
In the October crash of the Russian jetliner, the plane broke up in midair 23 minutes after takeoff from the Red Sea resort city of Sharm el Sheikh. The Islamic State, whose local affiliate is fighting the Egyptian military in the Sinai Peninsula, claimed that it had brought down the plane, an Airbus A321-200.
Egypt initially denied that the crash was connected to terrorism, even as Russia and Britain said that they believed a bomb was responsible. But in February, Mr. Sisi said that the flight had been brought down by terrorists, although he did not specify by which group.
The crash dealt a crippling blow to Egypt’s beleaguered tourism industry, which had already declined sharply in recent years. It also helped precipitate a decline in the value of the Egyptian currency in recent months.
Russia and Britain have suspended flights to Sharm el Sheikh since the crash. The Egyptian investigation has yet to officially identify the exact cause. But President Vladimir V. Putin of Russia and Mr. Sisi discussed the resumption of flights in a telephone call on May 10, according to a statement from the Kremlin.
The last major crash involving an EgyptAir plane occurred in 2002 when a Boeing 737 traveling to Tunis from Cairo crashed into a hill near the Tunis airport, killing 18 of the 62 people on board.
In March, a hijacker wearing a fake explosives vest diverted an EgyptAir domestic flight to the island of Cyprus, where an hourslong standoff result in his arrest and no injuries to passengers. The Cypriot authorities later described the man, Seif Eldin Mustafa, who said he wanted to free female prisoners from Egyptian jails, as “psychologically disturbed.” He is currently battling extradition to Egypt.
Security at Charles de Gaulle Airport outside Paris was tightened after the terrorist attacks in and around the French capital in November, and scrutiny of passengers and luggage was also stepped up in the wake of the bombing of Brussels Airport in March.
After the November attacks, French authorities have used the threat of terrorism to justify raids of employee lockers at Charles de Gaulle, as well as a systematic review of the roughly 87,000 airport employees who have badges giving them access to secure areas that include the tarmac, baggage handling and cargo storage. Those reviews have led the authorities to revoke dozens of badges for security reasons, according to the airport police.
Rules that ban passengers from carrying liquids, gels and aerosols in hand luggage were also extended to apply to airline and airport personnel as well as anyone with access to secure areas of the airport.
Egypt has come under criticism in the past for its lack of transparency in aviation accidents. In 1999, an EgyptAir flight crashed into the Atlantic Ocean shortly after takeoff from John F. Kennedy Airport in New York, killing all 217 people on board.
Although American investigators concluded that the co-pilot had steered the airplane in the sea, Egypt rejected the idea of suicide and still insists that the crash was caused by an unspecified mechanical failure.