CAIRO — A French ship searching the Mediterranean has detected black box signals from a missing EgyptAir flight in the waters between the Greek island of Crete and the Egyptian coast, a development that could help solve the mystery of why the aircraft crashed into the sea last month, killing all 66 on board.
The discovery, announced Wednesday, could help guide search teams to the wreckage and the flight’s data and cockpit voice recorders, which if retrieved unharmed could reveal whether a mechanical fault or a hijacking or bomb caused the disaster.
In the two weeks since Flight 804 disappeared from radar en route to Cairo from Paris, only small pieces of debris and human remains have been retrieved from the crash site. No terrorist group has claimed responsibility, though Egypt’s civil aviation minister, Sherif Fathi, has said terrorism is a more likely cause than equipment failure or some other catastrophic event.
The flight recorders will be critical to determining whether the disaster was caused by an accident or a deliberate act.
Equipped with sophisticated underwater sensors, the French naval vessel Laplace had been taking part in the search for the missing Airbus A320 since last week. On Wednesday, the Egyptian agency leading the inquiry into the crash said the ship had received signals “from the seabed of the wreckage search area, assumed to be from one of the data recorders.”
Hours later, the French company Alseamar confirmed that its equipment aboard the ship had detected signals from one of the black box recorders.
It said the naval vessel started searching for the signals at midday Tuesday, and “less than 24 hours were necessary . . . to locate signals from one of the recorders of flight MS804.”
The statement did not indicate how the company knew the signals were from the plane’s black box, and the French air accident investigation agency BEA said it was impossible to tell whether they were from the flight’s data or voice recorder.
But Sebastien Barthe, an agency spokesman, said the signal was specific enough to indicate that it came from one of the flight’s data recorders. BEA investigators are aboard the Laplace.
Locator pings emitted by flight data and cockpit voice recorders can be picked up from deep underwater. The Laplace is equipped with three detectors designed to pick up those signals, which in the case of the EgyptAir plane are believed to be at a depth of 9,842 feet. By comparison, the wreckage of the Titanic is lying at a depth of 12,500 feet.
A second ship, the John Lethbridge, equipped with sonar and other equipment capable of detecting wreckage at depths up to 6,000 feet, was to join the search later this week.
The EgyptAir Airbus A320 had been cruising normally in clear skies on an overnight flight on May 19 when it disappeared from radar and plunged 38,000 feet into the sea. A distress signal was never issued, the airline said.
Since the crash, only small pieces of wreckage and human remains have been recovered in a search that has been narrowed down to 3-mile area of the Mediterranean.
Locating the black boxes could significantly narrow the search site.
Hani Galal, a former EgyptAir pilot who has investigated other air disasters, said the flight recorders are located in a compartment under an aircraft’s tail, so finding them “means there is 90 percent probability that the wreckage, or at least the tail, will be found.”
“The tail is like the neck of the human body. It’s the weakest point and separates upon impact,” he said, a fact that can help protect the recorders from severe damage the rest of the aircraft might sustain.
Shaker Kelada, an EgyptAir official who has led other crash investigations for the carrier, said that Wednesday’s discovery meant that half “the job has been done now” and that the next step would be to determine the black boxes’ exact location and extract them from the sea.
“We have to find where the boxes are exactly and decide on how to pull them out,” he said, adding that search teams might need to send in robots or submarines and “be extremely careful . . . to avoid any possible damage.”
Tawfiq al-Assi, a former head of EgyptAir and a pilot himself, said the search teams would face a challenge in finding robots that can work thousands of meters under the sea.
Galal said after determining the location of the recorders, the second mission would be to photograph the recorders and the wreckage to determine how to retrieve them. “Are the recorders and the tail in a position that enables robots to pull them out, or are they buried under the bulk of the plane?” he said.
In addition to the black boxes, he said investigators would need at least 70 percent of the wreckage to reconstruct the plane and try to determine the cause of the crash.
No hard evidence has emerged so far about what caused the disaster, though earlier leaked flight data indicated a sensor had detected smoke in a lavatory and a fault in two of the plane’s cockpit windows in the final moments of the flight.
Al-Assi said that if there is a “clear voice segment” on the voice recorder, it could point to what happened during the final minutes before the plane crashed. The flight data recorder shows all technical information related to the aircraft until the final second, a crucial fact when “seconds matter,” he said.
Safety onboard Egyptian aircraft and at the country’s airports has been under close international scrutiny since a Russian airliner crashed in the Sinai Peninsula last October, killing all 224 people on board, shortly after taking off from an Egyptian resort.
That crash — claimed by the Islamic State group’s affiliate in the Sinai and blamed by Moscow on an explosive device planted on board — decimated Egypt’s tourism industry, which had already been battered by years of turmoil in the country.
On Wednesday, Egyptian authorities said they had evacuated all passengers aboard an EgyptAir flight scheduled to depart Tuesday night from Cairo for Bangkok after receiving a report of a bomb on board.
Tarek Zaki, head of security at Cairo airport, said the warning claimed an unidentified assailant had planted a bomb on the plane. A security official, speaking on condition of anonymity in line with regulations, said the plane and baggage were searched but no bomb was found. The threat caused a delay and eventually led to the flight being cancelled.
Corbet reported from Paris.