New clues emerged Friday about EgyptAir Flight 804, but there were no answers as to what caused the plane to go down in the Mediterranean Sea.
There were smoke alerts near the airliner cockpit early Thursday in the minutes before it crashed, according to flight data CNN obtained Friday from an Egyptian source.
The data came through the Aircraft Communications Addressing and Reporting System (ACARS), a data link for sending messages between planes and ground facilities. A screen grab of data has time stamps that match the approximate time the aircraft went missing.
The alerts don't necessarily mean a fire occurred on the plane or that the crew even knew about the alerts, which are automatically transmitted, aviation experts cautioned.
Still missing are the most important clue: the flight data and cockpit voice recorders, sometimes called the "black boxes."
"(The data) doesn't tell us anything, whether it's an explosion because of a bomb or because of a mechanical fault, but immediately it narrows down the area that we're looking at," CNN aviation analyst Richard Quest said. "We're now no longer worried about wings or what else might have happened, or other flight control surfaces."
The plane carrying 66 people disappeared while flying from Paris to Cairo.
Egyptian officials say they suspect terrorism, but no group has come forward to claim credit.
No survivors have been found, but searchers in the Mediterranean Sea located debris on Friday, including suitcases and human remains.
Data sent over a few minutes
Aviation experts held different views of what the ACARS data may signify.
There were indications of problems with a heated window in the cockpit, a sliding window in the cockpit, smoke in the lavatory, smoke in the avionics compartment below the cockpit, a fixed window, the auto pilot and the flight control system.
"It could have been either something mechanical that had failed, a short circuit, or it could have been an incendiary device of some kind as well," CNN aviation analyst David Soucie said.
He said it was significant that the data was sent over a period of one to two minutes.
"Now if it it was a bomb, the characteristic bomb ... (it) would have ruptured the skin of the aircraft," Soucie said. "This is not the indication you would have had, because a bomb that would do that would be instantaneous, and these reports would not have gone over two minutes like they do."
According to an aviation official and a former FAA official, the ACARS data, however, could be consistent with a catastrophic failure -- be it from an intentional act or mechanical breakdown.
The aviation official said if there was a fire on board a plane, it would tend to burn slow enough for pilots to send an emergency message. These messages could have been a result of wires shorting out and malfunctioning as the plane broke apart.
The aviation official said the messages, while random, would be consistent with what would be sent by a system on a plane that is falling apart.
There have been electrical problems with window anti-ice heaters in A320s. In 2003, the FAA required windshields replaced in all A320s in the United States. It's not known whether Egypt followed the FAA directive.
Debris found in water
EgyptAir and Greek officials said Friday that searchers have found debris from the plane in the water.
Greek Defense Minister Panos Kammenos relayed the Egyptian discovery of the body part, seats and suitcases, citing Egyptian officials. Later, the airline issued a statement saying more remains, personal belongings and aircraft seats had been discovered.
The Egyptian military said it had found parts of the aircraft and passenger belongings about 290 kilometers (180 miles) north of the coastal city of Alexandria, Egypt.
What went wrong?
The plane was carrying 56 passengers and 10 crew members and security when it left Charles de Gaulle Airport in Paris late Wednesday.
Most of the passengers were Egyptian -- 30 in all. But also aboard were 15 French citizens, including an infant. There were also passengers from Iraq, Britain, Belgium, Kuwait, Saudi Arabia, Sudan, Chad, Portugal, Canada and Algeria, according to the Egyptian aviation minister.
It disappeared from radar early Thursday as it flew to Cairo -- what should have been about a 3½-hour flight.
At some point before dropping off radar, the plane swerved 90 degrees to the left and then made a 360-degree turn to the right before plunging first to 15,000 feet, then 10,000 feet, and disappearing from radar, Greek officials said.
That sudden change in what had been an uneventful flight is why Egyptian officials are focusing on terror as the likely cause, a senior Egyptian official told CNN on Friday.
What Greek officials described as swerving was likely pieces of the aircraft being picked up on radar as they fell from the sky, U.S. officials told CNN.
As of now, investigators have found nothing implicating the flight crew or security officials aboard the plane, the Egyptian official said.
Checks of the passenger manifest have so far resulted in no hits on terror watch lists, officials with knowledge of the investigation said.
The jet had routine maintenance checks in Cairo before it left for Paris, the airline said. Earlier Wednesday, the jet was also in Eritrea and Tunisia, data from flight tracking websites show.
Greece, France, the United States and other nations were searching about 130 nautical miles southeast of the Greek island of Karpathos, Greek aviation officials said.
The European Space Agency said Friday that its Sentinel-1A satellite had spotted a 2-kilometer (1.24-mile) oil slick near where the plane is believed to have crashed. The agency said it's possible the slick could be from another source.
As crews searched, somber relatives gathered in Cairo and Paris airports, seeking word on their loved ones.
The Egyptian Civil Aviation Ministry has formed an investigative committee to look into the crash.
It will be led by Ayman al-Moqadem, the investigator who is also heading up the inquiry into the October crash of a Russian Metrojet airliner over the Sinai, the agency said in a statement. That disaster, which killed all 224 aboard, is widely believed to be the work of terrorists.
Earlier Friday, three French technical safety investigators and a technical expert from airplane manufacturer Airbus arrived in Cairo to help with the investigation, according to the French Embassy in Egypt.