A SEA-crusted wing part washed up on an island in the western Indian Ocean might be the first trace of Malaysia Airlines Flight 370 since it vanished nearly 18 months ago, and a tragic, but finally solid clue to one of aviation’s most perplexing and expensive mysteries.

Malaysia’s prime minister said yesterday that the debris found on the French island of Reunion will be sent for investigation to the French city of Toulouse, the center for European aviation.

“We have had many false alarms before, but for the sake of the families who have lost loved ones, and suffered such heartbreaking uncertainty, I pray that we will find out the truth so that they may have closure and peace,” Najib Razak said on his personal blog.

Najib promised to make any new information public quickly.

Air safety investigators — one of them a Boeing investigator — have identified the component as a “flaperon” from the trailing edge of a Boeing 777 wing, a United States official said.

Flight 370, which disappeared on March 8, 2014, with 239 people on board, is the only 777 known to be missing.

“It’s the first real evidence that there is a possibility that a part of the aircraft may have been found,” said Australian Transport Minister Warren Truss, whose country is leading the search for the plane in a remote patch of ocean far off Australia’s west coast.

“It’s too early to make that judgment, but clearly we are treating this as a major lead,” he said.

Flight 370 had been traveling from Kuala Lumpur to Beijing, but investigators believe based on satellite data that the plane turned south into the Indian Ocean after vanishing from radar. If the wing part is from the Malaysian plane, it would bolster that theory and put to rest others that it traveled north, or landed somewhere after being hijacked.

The wing piece is about 2 meters long. Investigators have found a number on the part, but it is not a serial or registration number, Truss said.

It could be a maintenance number, which might help investigators figure out what plane it belongs to, he said.

A French official close to an investigation of the debris confirmed on Wednesday that French law enforcement officers are on Reunion to examine it.

A French television network was airing video from its Reunion affiliate of the debris, while US investigators are examining a photo of the debris.

The US and French officials spoke on condition that they not be named because they aren’t authorized to speak publicly.

Flaperons are located on the rear edge of both wings, about midway between the fuselage and the tips. When the plane is banking, the flaperon on one wing tilts up and the other tilts down, which makes the plane roll to the left or right as it turns.

The piece could help investigators figure out how the plane crashed, but whether it will help search crews pinpoint the rest of the wreckage is unclear, given the complexity of the currents in the southern Indian Ocean and the time that has elapsed since the plane disappeared.

A massive multinational search effort of the southern Indian Ocean, the South China Sea and the Gulf of Thailand has turned up no trace of the plane.

The last primary radar contact with Flight 370 placed its position over the Andaman Sea about 370 kilometers northwest of the Malaysian city of Penang. Reunion is about 5,600km southwest of Penang, and about 4,200km west of the current search area.

It was well understood after the aircraft disappeared that if there was any floating debris from the plane, Indian Ocean currents would eventually carry it to the east coast of Africa, said aviation safety expert John Goglia, a former member of the US National Transportation Safety Board.

However, the debris is unlikely to provide much help in tracing the ocean currents back to the location of the main wreckage, he said.

“It’s going to be hard to say with any certainty where the source of this was,” he said.

“It just confirms that the airplane is in the water and hasn’t been hijacked to some remote place and is waiting to be used for some other purpose ... We haven’t lost any 777s anywhere else.”

In a statement yesterday, the prefecture of Reunion emphasized that the source of the debris has not been identified, nor has it been definitely found to be from a Boeing 777. Authorities there have asked France’s aviation investigative agency, known as the BEA, to coordinate with international investigators, notably the Malaysian and Australian authorities.

The discovery is unlikely to alter the seabed search, said Australian Transport Safety Bureau Chief Commissioner Martin Dolan, who is heading up the hunt. If the find proves to be part of the missing aircraft, it would be consistent with the theory that the plane crashed within the 120,000-square-kilometer search area, 1,800km southwest of Australia, he said.

“It doesn’t rule out our current search area if this were associated with MH370. It is entirely possible that something could have drifted from our current search area to that island,” he said.

Search resources would be better spent continuing the seabed search with sonar and video for wreckage rather than reviving a surface search for debris if the part proves to be from Flight 370, he said.

Robin Beaman, a marine geologist at Australia’s James Cook University, said there is precedence for large objects traveling vast distances across the Indian Ocean. Last year, a man lost his boat off the Western Australia coast after it overturned in rough seas. Eight months later, the boat turned up off the French island of Mayotte, west of Madagascar — 7,400km from where it disappeared.

“I don’t think we should rule anything out, that’s for sure,” Beaman said.

He said he believes experts could analyze ocean currents to try to determine where the plane entered the water, though given the time that has elapsed and the vast distance the debris might have traveled, it would be very difficult.

If the part belongs to Flight 370, it could provide valuable clues to investigators trying to figure out what caused the aircraft to vanish in the first place, said Jason Middleton, an aviation professor at the University of New South Wales in Sydney.

The nature of the damage to the debris could help indicate whether the plane broke up in the air or when it hit the water, and how violently it did so, he said.

The barnacles attached to the part could also help marine biologists determine how long it has been in the water, he said.

A comprehensive report earlier this year into the plane’s disappearance revealed that the battery of the locator beacon for the plane’s flight data recorder had expired more than a year before the jet vanished.

However, the report said the battery in the locator beacon of the cockpit voice recorder was working.

Over the past 16 months, hopes have repeatedly been raised and then dashed that the plane, or parts of it, had been found: Objects spotted on satellite imagery, items found floating in the sea, oil slicks — in the end, none of them were from Flight 370.