While it is too soon to say why the EgyptAir plane disappeared off the radar, a terrorist attack is more likely than technical issues, Egypt's Aviation Minister says.
A massive search is continuing for a second day for the EgyptAir plane that disappeared over the Mediterranean.
Greek, Egyptian, French and UK military units are taking part in the operation near Greece's Karpathos island.
Flight MS804 was en route from Paris to Cairo with 66 passengers and crew when it vanished early on Thursday (local time).
Greece said radar showed the Airbus A320 had made two sharp turns and dropped more than 25,000ft (7620m) before plunging into the sea.
Greece's defence minister Panos Kammenos said the Airbus A320 had "turned 90 degrees left and then a 360-degree turn to the right", before disappearing from radar.
Egypt's Aviation Minister Sharif Fathy said the plane was more likely to have been brought down by a terrorist act than a technical fault.
Most of the people on board Flight MS804 were from Egypt and France. A Briton was also among the passengers.
So far, no wreckage or debris from the aircraft has been found.
Debris not from EgyptAir plane - airline
Initial reports late on Thursday based on Egyptian officials that wreckage had been found proved unfounded.
Debris, including "floating material" and lifejackets found in the Mediterranean Sea is not from the EgyptAir plane, the airline now says.
The airline had said searchers found wreckage in the sea off Karpathos Island and that the country's civil aviation ministry had confirmed it was from the AirbusA320 which vanished.
But EgyptAir vice president Ahmed Adel told CNN that the wreckage had not been found.
"We stand corrected on finding the wreckage because what we identified is not a part of our plane. So the search and rescue is still going on," he said.
Greek officials had already cast doubt on the debris being from the flight. Air accident investigator Athanasios Binis told the BBC it was not from the plane, and Greek sources told Reuters the material found so far was not blue and white - the EgyptAir colours.
Egyptian Prime Minister Sherif Ismail said it was too early to rule out any explanation for the crash, including an attack like the one blamed for bringing down a Russian airliner over Egypt's Sinai Peninsula last year.
Egypt's aviation minister Sherif Fathi said the possibility of a terror attack was stronger than technical failure.
"Let's not try to jump to the side that is trying to identify this as a technical failure - on the contrary.
"The situation may point - and I say 'may' because I don't want to speculate and I don't want to go to assumptions like others - but if you analyse the situation properly, the possibility of having a different action, or having a terror attack, is higher than the possibility of having a technical [fault]."
According to Greece's civil aviation chief, calls from Greek air traffic controllers to flight MS804 went unanswered just before it left Greek airspace, and it disappeared from radar screens soon afterwards.
Greek air traffic controllers had spoken to the pilot 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 said.
- The plane was travelling from Paris to Cairo, and faded from radar 10 miles after entering Egyptian airspace, about 2.30am local time
- 56 passengers and 10 crew were on board Airbus A320
- 30 Egyptians and 15 French nationals were on the plane, and a number of people from different nationalities. No New Zealanders are believed to have been on board
- Distress call was made about 4.26am local time, Egypt's military says - but the Civil Aviation Authority later said that wasn't true
- Rescue teams have been searching the area 50km off the Egyptian coastline
There was no official indication of a possible cause, whether technical failure, human error or sabotage. Ultra-hardline Islamists have targeted airports, airliners and tourist sites in Europe, Egypt, Tunisia and other Middle Eastern countries over the past few years.
Asked if he could rule out terrorist involvement, Egyptian Prime Minister Sherif Ismail told reporters: "We cannot exclude anything at this time or confirm anything. All the search operations must be concluded so we can know the cause."
French President Francois Hollande also said the cause was unknown. "No hypothesis can be ruled out, nor can any be favoured over another."
- RNZ / Reuters / BBC