Egyptian authorities have found luggage, a seat and a body part during the search for an EgyptAir jet which plunged into the Mediterranean, Greece's defence minister says.

"A short while ago we were briefed by the Egyptian authorities ... on the discovery of a body part, a seat and baggage just south of where the aircraft signal was lost," Defence Minister Panos Kammenos told reporters in Athens on Friday.

The flight with 66 people on board and travelling from Paris to Cairo vanished minutes after leaving Greek for Egyptian airspace early on Thursday morning.

Kammenos said Greece could not speculate on the reasons the aircraft crashed. He reiterated that Greek radars picked up sharp swings in its trajectory as it plunged from a cruising altitude to 15,000 feet, then vanished from radar.

Earlier the Egyptian army said on its official Facebook page wreckage from the missing plane had been found 290km north of the Mediterranean Sea city of Alexandria.

"The Egyptian aircraft and ships also found [Friday] morning personal items of some passengers of the plane," the army said in the statement.

Three French aviation accident investigators and an Airbus technical expert have arrived in Cairo on Friday to join the Egypt-led probe.

The reasons for the disappearance are currently unknown.

Search operations are under way to locate the jet's two black boxes.

Egyptian military pilots search for the wreckage of the missing EgyptAir flight. (AFP)

Distressed relatives of those on board have begun to gather at Charles de Gaulle Airport. (AAP)