CAIRO — The EgyptAir red-eye from Paris to Cairo, an Airbus A320 jetliner less than half full, had just entered Egyptian airspace early Thursday on the final part of its journey.
Suddenly the twin-engine jetliner jerked hard to the left, then hard to the right, circled and plunged 28,000 feet, disappearing from the radar screens of Greek and Egyptian air traffic controllers.
That began a day of emergency rescuers scrambling, officials issuing conflicting information and experts speculating about the fate of EgyptAir Flight 804, which carried at least 66 people from roughly a dozen nations and was presumed to have crashed into the Mediterranean Sea.
EgyptAir initially said wreckage of the plane had been found with the help of searchers from Greece, but a senior official of the airline speaking on CNN retracted that assertion hours later. Egyptian officials suggested that terrorism was a more likely cause for the disappearance than mechanical failure, but others cautioned that it was premature to make that judgment.
The loss of the flight was the second civilian aviation disaster to hit Egypt in the past seven months. It resurrected fears and speculation about the safety and security of Egyptian aviation, which has a history of lapses — as well as the specter of a security breach in Paris, where the plane took off.
The mystery of the plane’s demise also raised broader questions about the vulnerability of civilian air travel to terrorism. Flight 804 went missing against the backdrop of threats from militant extremist groups like the Islamic State and al-Qaida, with networks linking Europe to the Middle East.
By Thursday evening, no group had claimed responsibility.
With differing reports about precisely what wreckage had been discovered, President Abdel-Fattah el-Sissi of Egypt ordered the armed forces to “take all measures necessary” to find the remains of the plane, his office said in a statement.
The statement also said work had begun immediately “to unravel the circumstances surrounding the disappearance of the Egyptian aircraft and establish its causes.”
As news of the missing plane spread in Cairo, relatives of those aboard rushed to the airport, some overcome with grief and anger over the lack of information.
“Pray for them,” said a relative of a flight attendant who had just married. “We don’t know anything.”