The wing fragment that washed ashore last week on a remote Indian Ocean beach is a piece of the Malaysia Airlines jetliner that disappeared under mysterious circumstances more than 16 months ago, Malaysian Prime Minister Najib Razak said Wednesday.

“The international team of experts have conclusively confirmed that the aircraft debris found on Reunion Island is indeed from MH370,” Najib said in a statement. Malaysia Airlines issued a statement calling the confirmation “a major breakthrough” in the search for the plane.

The piece, known as a flaperon, was being examined in a French laboratory, and authorities in Paris were more cautious in their confirmation that it came from a Boeing 777.

There were “very strong indications” that the piece of the wing was from Flight 370 for “two reasons,” French prosecutor Serge Mackowiak said at a Paris news conference.

He said that representatives from Boeing “confirmed that the flaperon did come from a 777 because of its specific characteristics, such as the structure and the color.” And he said Malaysia Airlines provided documentation on the plane that allowed French investigators to “match the piece that we examined and the flaperon of that particular flight — the characteristics match.”

What happened to Flight 370?

He also said details still needed to be confirmed “by further analysis that will start [Thursday] at the laboratory.”

Confirmation that the wing fragment came from the missing aircraft establishes that Flight 370 crashed somewhere in the Indian Ocean, laying to rest conspiracy theories that it had been diverted to a desert island by hijackers or spirited off to a foreign country for use as some sort of political bargaining chip.

It does not, however, provide much help to those who are searching for the rest of the airplane and the remains of the 239 people who were on board.

“The burden and uncertainty faced by the families during this time has been unspeakable,” Najib said. “It is my hope that this confirmation, however tragic and painful, will at least bring certainty to the families and loved ones of the 239 people on board.”

Nancy Smyth, dean of the department of social work at the University at Buffalo called the confirmation important to the families but added, “There are still many questions because they still don’t know what happened.”

“For the families, in an ideal world, it would not be finding a wing fragment, but it would be finding bodies,” she said. “So much of our grieving process involves physicality — seeing a body in a coffin. Without that, it is very hard to start the grieving process. Without that, families will always hold on to some sort of hope that their loved ones are sitting on an island somewhere.”

The wing piece was found last week by a crew cleaning debris from a rocky, little-used beach on Reunion Island, a French possession that is closer to Africa than the search area off Australia.

Flight 370 went radically off course en route from Kuala Lumpur to Beijing on March 8, 2014, vanishing from radar screens and ending radio contact. Investigators used satellite echoes and other means to surmise that it flew to a remote area roughly 1,000 miles off the western coast of Australia before crashing into the sea.

The search largely has been shut down recently as seas became more rambunctious during the winter months in the Southern Hemisphere. But it will resume with vigor renewed by finding the wing fragment when spring arrives.

The search area lies almost 3,000 miles to the east of Reunion Island and would be considered enormous to search even if it were a piece of dry land without tree cover. But most of the plane is believed to be sitting 1 1/2 to 2 1 / 2 miles below the ocean surface, likely nestled somewhere in a jagged undersea mountain region. That underwater terrain is known as the Southeast Indian Ridge, a portion of an underwater mountain chain that spans the globe, and the terrain has been likened in stature to the Appalachian mountain range in the United States.

The search area has been expanded to nearly the size of South Dakota. Although searchers have numerous tools, two of the most effective — sonar towed from a ship and unmanned mini-submarines — move at about the speed of a Roomba vacuum cleaner, capable of scouring only tiny sections of the sea floor each day.

When they announced the search area expansion in June, Australian officials who are leading the hunt said “in the absence of credible new information that leads to the identification of a specific location of the aircraft,” it wouldn’t be changed.

The Australian coordinating the search, Martin Dolan, confirmed Monday that discovery of the wing fragment would not change the search area.

Australian Deputy Prime Minister Warren Truss elaborated on that this week.

“The experts are telling us that there is a 97 percent possibility that it is in that area, and if you move into a wider area there is just too much to be covered for a small chance of finding the aircraft,” he told the Wall Street Journal.

Sea life that has attached itself to the wing section may provide some clues as to the path it took during more than 500 days floating about the Indian Ocean. Different types of marine life exist in swaths of the ocean, so seeing what has adhered to the piece may reveal the route it took in the prevailing counter-clockwise currents of the Indian Ocean.

Piecing the plane’s erratic path together through radio and satellite echoes gave authorities a general area in which to search but provided no evidence of why it ended up there. Flight 370 made several sharp turns, suggesting that someone was at the controls, rather than an autopilot.

But even if the body of the plane is found, the so-called black box is unlikely to reveal what happened in the cockpit after it went dramatically off course northeast of the Malaysian coast line. The cockpit voice recorder, which might have revealed that, is on two-hour loop and the plane is estimated to have flown for about eight hours before crashing. Anything said as the plane diverted from its course would have been recorded over by the time it went down.

The other half of the black box, the flight data recorder, could provide important details to help authorities determine what went wrong and what ultimately caused the plane to go down. One theory holds that the plane suffered a loss of cabin and cockpit pressurization, which rendered all on board unconscious in the final hours of flight. The data recorder would indicate that, as well as whether the plane finally went down when it ran out of fuel.

Experts who theorize the plane was diverted by cockpit crew or hijackers point to several purposeful actions that occurred before the plane disappeared from radar. Notably, the plane took turns off its intended flight path, ultimately putting it on a heading for the Indian Ocean, and it appeared the electronics that allowed the plane to be tracked were deliberately turned off.

One speculative concept gained enough traction to earn a label: “the rogue pilot theory.” It suggests that pilot Zaharie Ahmad Shah, 53, was distraught, perhaps over marital problems. He locked the co-pilot out of the cockpit, turned off the key tracking electronics, piloted the aircraft on a course for the Indian Ocean and then shut off cabin pressurization, suffocating himself and everyone on board hours before the plane ran out of fuel and crashed.

Although Malaysian officials have said the plane’s disappearance appeared to be a “deliberate act,” investigators produced a 584-page interim report in March that said there no evidence to suggest that either pilot or co-pilot were responsible.

Investigators found nothing in his background to suggest he was depressed, had financial problems or was contemplating suicide.

“The Captain’s ability to handle stress at work and home was good,” the report said. “There was no known history of apathy, anxiety, or irritability. There were no significant changes in his lifestyle, interpersonal conflict or family stresses. There were no behavioral signs of social isolation, change in habits or interest, self-neglect, drug or alcohol abuse of the captain, first officer and the cabin crew.”

Investigators compared a video of the pilot boarding the flight with videos taken as he boarded his two previous flights. They concluded: “No significant behavioural changes observed . . . the appearance was similar, i.e. well groomed and attired. The gait, posture, facial expressions and mannerism were his normal characteristics.”

The investigators also reviewed the backgrounds of everyone on board without raising any suspicions that crew and passengers were terrorists. And had terrorists struck, they said, radio transmissions and transponder sending radar tracking data would not have ended so abruptly.

Although the wing fragment offers no clues as to what happened on board, its condition may provide hints of whether the plane crashed because of a fire or explosion, or hit the water after running out of fuel.