An EgyptAir jet carrying 66 passengers and crew from Paris to Cairo disappeared from radar over the Mediterranean Sea after swerving in mid-air and plunging from cruising height, Greek authorities say.

Key points: There were 53 adult passengers, two infants, one child and 10 crew members on board

There were 53 adult passengers, two infants, one child and 10 crew members on board Greece says plane made "swerve and descent" before vanishing in Egyptian air space

Greece says plane made "swerve and descent" before vanishing in Egyptian air space Egyptian military search and rescue teams combing the area where the jet might have gone down

The plane was 16 kilometres into Egyptian air space when it disappeared from the radar about 2:45am (local time) and Greek and Egyptian search and rescue teams were combing the area where the jet might have gone down.

French President Francois Hollande confirmed the aircraft "came down and is lost", but said it was too early to rule out any explanation.

However, Egypt's Civil Aviation Minister Sharif Fathy said a terrorist attack was more likely to have taken down the airliner than a technical failure. But there were no known security issues with the flight and no evidence to point to foul play.

Greek Defence Minister Panos Kammenos said the airliner made "sudden swerves" and plunged before dropping off radars over the southern Mediterranean.

He said the Airbus A320 had first swerved 90 degrees to the left, then spun through 360 degrees to the right. After plunging from 37,000 feet to 15,000, it vanished from Greek radar screens.

The flight path and last known location of EgyptAir flight MS804. ( ABC News: Tim Leslie )

Flight MS804 was carrying 56 passengers, including one child and two infants, and 10 crew, EgyptAir said.

They included 30 Egyptian and 15 French nationals, along with nationals from 10 other countries. No Australians were believed to be onboard.

Families of passengers and Egyptian Prime Minister Sherif Ismail rushed to Cairo International Airport shortly after dawn while the Egyptian and Greek military scrambled aircraft and boats to search for the plane.

Greece said it had deployed aircraft and a frigate to the area to help with the search.

No hypothesis can be ruled out: Hollande

Mr Hollande said it was too early to say what caused the aircraft to disappear, but that it seemed likely it had "crashed".

"Unfortunately the information we have ... confirms to us that the plane came down and is lost," Mr Hollande said.

"No hypothesis can be ruled out, nor can any be favoured over another.

"We feel solidarity and compassion. It's not the first such catastrophe, and we know what it means for families and loved ones."

The French President expressed his solidarity with the families of those onboard. ( AFP: Khaled Desouki )

Mr Hollande said French, Egyptian and Greek authorities were working together to locate the aircraft as Paris prosecutors separately confirmed they had launched an investigation into the incident.

Greek air traffic controllers spoke to the pilot of flight MS804 over the island of Kea, in what was thought to be the last broadcast from the aircraft.

"The pilot did not mention any problems," Kostas Litzerakis, the head of Greece's civil aviation department, told Reuters.

The Egyptian army has denied an EgyptAir claim that it received an emergency signal — possibly from an emergency beacon attached to the plane used to help locate flight recorders in water — two hours after it disappeared from radar screens.

Weather was clear at time of disappearance

The weather was clear at the time the plane disappeared, according to weather reports, and speed and altitude data from aviation website FlightRadar24.com indicated the plane was cruising at the time it disappeared.

EgyptAir Airbus A320 disappeared while flying from Paris to Cairo. ( Supplied: Flikr/Kurush Pawar )

Under UN aviation rules, Egypt will automatically lead an investigation into the accident assisted by countries including France.

An Airbus A321 operated by Russia's Metrojet crashed in the Sinai on October 31 last year, killing all 224 people on board.

Russia and Western governments have said the plane was likely brought down by a bomb, and the Islamic State militant group said it had smuggled an explosive device on board.

In March, an EgyptAir plane flying from Alexandria to Cairo was hijacked and forced to land in Cyprus by a man with what authorities said was a fake suicide belt. He was arrested after giving himself up.

Reuters