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.

EgyptAir said it last made contact with the plane at 2:30 a.m.

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,” Mohamed Samir, a military spokesman, said.

Greece said it sent two aircraft — a C-130 and an early-warning aircraft — to the area.

There was no immediate indication of what 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.