Debris from the EgyptAir flight that crashed into the Mediterranean was found on Friday by the Egyptian military.
Some human remains, along with two airplane seats and at least one suitcase were also found, according to the Greek defense minister.
There are still many unknowns, but it looks very unlikely that any of the 66 people on board flight MS804 survived.
So far, no terrorist groups have issued any credible claims of responsibility for the crash. In the past, groups like ISIS and Al Qaeda have been quick to take credit for acts of terror.
In Egypt, the country's top aviation official Sherif Fathy said he could not rule out either terrorism or a technical problem, but he was leaning toward the former explanation.
"If you analyse the situation properly, the possibility of having ...a terror attack, is higher than the possibility of having a technical [one]," Fathy said.
Soon after that, the plane disappeared from radar screens, according to the Greek Defense Minister, Panos Kammenos.
Egyptian and Greek officials said they had dispatched aircraft and naval vessels on a search mission. They were expected to be joined by French and American teams.
People on board the flight included 30 Egyptians, 15 French citizens, two Iraqis, two Canadians, and one person each from Algeria, Belgium, Britain, Chad, Kuwait, Portugal, Saudi Arabia and Sudan.
But both France and Egypt have come under attack by extremists from the violent extremist group ISIS over the past year.
Egypt's president Abdul Fattah al-Sisi has ordered the country's civil aviation ministry and military to take all necessary measures to locate debris from the missing plane. Sisi ordered an investigation into the cause of the crash as suspicions swiftly focused on a bomb.
The French president, Francois Hollande has also called for a comprehensive investigation.
"We must ensure that we know everything on the causes of what happened. No hypothesis is ruled out or favored," the French president said in a televised address Thursday.
"Whether it was an accident or another hypothesis that everyone has on their mind — a terrorist hypothesis ... at this stage we must focus on our solidarity with the families and the search for the causes of the catastrophe."
ISIS has been waging a deadly insurgency against Egyptian security forces and last October claimed the bombing of a Russian airliner flying home holidaymakers from the Egyptian resort of Sharm El-Sheikh, which killed all 224 people on board.
France earlier called a crisis meeting of top ministers as Prime Minister Manuel Valls said "no theory can be ruled out" to explain the plane's disappearance.
EgyptAir said contact was lost with the flight about 175 miles north of the Egyptian coast.
No distress call
Greek civil aviation chief Constantinos Litzerakos said the pilot had mentioned no problem in the last communication, which came several minutes before the plane disappeared.
"The flight controllers contacted the pilot [with the plane] at a height of 37,000 feet [near Athens] ... he did not mention a problem," Litzerakos told Greece's Antenna TV.
"We tracked the entire process from the plane's entry [into Greek airspace] to its exit, it does not appear to deviate at all from the coordinates we gave," he said.
EgyptAir Holding Company vice president Ahmed Adel also said there had been "no distress call" before the plane vanished.
"Airplanes do not fall out of the sky for no reason," says former Obama Administration counterterrorism official Juliette Kayyem. "And there are a limited number of reasons at this stage. One is catastrophic mechanical failure. The second is pilot error."
"The third [possibility] is something we don't have to call terrorism, but it is deliberative, whether it is a passenger or pilot or something put on the plane through luggage or at an airport facility."
Kayyem says there is only way for countries to respond to crises: with full transparency.
"This is not about Egypt. It is not about EgyptAir. It is not about the future of tourism in Egypt. It is about the people who lost their lives and their family members and it is also about the future." She says it is also about the safety and security of the global airline industry. "Are there gaps in security? Where are those gaps and how do we close them?"
Kayyem says shutting down the airline industry is not an option. "We live in a global environment and a global aviation environment in which you cannot stop airline travel while we wait to figure this out."
She says examining the physical evidence will reveal a lot. "The debris will give some clue as to whether there are explosives and then the search for this black box that we are always searching for."
Two babies among passengers
The passengers included a young boy and two infants.
Seven crew members and three security men were also on board.
EgyptAir said the plane had been manufactured in 2003. Airbus said it had clocked up 48,000 flight hours.
EgyptAir hit the headlines in March when a flight from the Egyptian coastal city of Alexandria to Cairo was hijacked and forced to divert to Cyprus, where the hijacker, who was described as "unstable," demanded to see his ex-wife.
He had claimed he was wearing an explosive vest, which turned out to be fake.
Last October, foreign governments issued travel warnings for Egypt and demanded a review of security at its airports after the Islamic State group downed the Russian airliner with what it said was a bomb concealed in a soda can that had been smuggled into the hold.
The disappearance of the EgyptAir jet comes more than two years after the start of one of the most enduring mysteries in aviation history.
Malaysia Airlines Flight MH370 vanished on March 8, 2014 en route from Kuala Lumpur to Beijing with 239 passengers and crew on board, mostly Chinese and Malaysians.
Authorities believe the Boeing 777 detoured to the remote southern Indian Ocean and then plunged into the water.
Matthew Bell and Carol Hills of PRI's The World and AFP's Samer al-Atrush in Cairo contributed to this report.