JUDY WOODRUFF: An airliner is lost with 66 people on board, setting off a frantic hunt for clues.

As the day ended in the Eastern Mediterranean Sea, the fate of a missing Egyptian Air passenger plane was anything but clear. And there was the suggestion of a terrorist connection.

John Yang begins our coverage.

JOHN YANG: There was heavy security at Charles de Gaulle Airport outside Paris, where EgyptAir Flight 804 took off last night headed for Cairo, where today families of those on board left the airport in a daze.

MAN (through interpreter): They don't have any information. They don't have specific information.

JOHN YANG: The Greek defense minister said all seemed normal as the plane flew through his nation's airspace before vanishing from radar.

PANOS KAMMENOS, Greek Defense Minister (through interpreter): At 3:37, the plane, which was 10 to 15 miles inside Egyptian airspace, at 37,000 feet, made a 90-degree turn to the left, and then a 360-degree turn towards the right, descending from 37,000 feet to 15,000 feet. The picture we had was lost at 10,000 feet.

JOHN YANG: Debris was spotted in the Mediterranean near the Greek island of Karpathos, although it wasn't clear if it was from Flight 804.

Egypt's aviation minister pointed to terrorism.

SHERIF FATHY, Egyptian Aviation Minister: If you analyze the situation properly, the possibility of having a different action or having a terror attack is higher than the possibility of having a technical…

JOHN YANG: This is only the latest in a series of incidents involving Egyptian aviation. In March, a man wearing a fake suicide belt hijacked EgyptAir Flight 181 to Cyprus. And last October, a Russian airliner exploded over the Sinai Desert after taking off from Sharm el-Sheikh. All 224 people aboard died in what Egyptian officials said was a terrorist attack.

In the past two days, the plane lost today flew round-trips between Cairo and Eritrea and Cairo and Tunis. Egyptian President Abdel Fattah El-Sisi convened an emergency meeting of advisers. So did French President Francois Hollande.

In Brussels, Secretary of State John Kerry expressed U.S. condolences.

JOHN KERRY, Secretary of State: The United States is providing assistance in the search effort, and relevant authorities are doing everything they can to try to find out what the facts are of what happened today.

JOHN YANG: The U.S. Navy deployed a P-3 Orion reconnaissance aircraft to help in the search for the wreckage, which could hold vital clues to what brought down Flight 804.

For the "PBS NewsHour," I'm John Yang.

JUDY WOODRUFF: Tonight, an Egyptian Air official said that no debris from the missing airplane has been found, correcting an earlier statement.