Experts have determined the wing fragment is from missing MH370.
The sister of a New Zealander lost on flight MH370 said it had been a sleepless night for his wife and family - but it's nothing they haven't been through before.
Overnight, Malaysian Prime Minister Najib Razak confirmed the wreckage found on the French-administered island of Reunion was that of MH370.
But just a few hours later French prosecutor Serge Mackowiak would not confirm the wreckage was from the missing Malaysia Airlines flight, only saying there was "strong supposition" that was the case.
Sara Weeks, the sister of Paul Weeks, who was on the doomed flight last March said it was an "emotional day" for his wife Danica in Australia and the rest of the family in New Zealand.
She said Danica had been up since at least 1.30am in Perth when she heard the news.
Ms Weeks said the news was not closure - especially for Danica who was still unable to tell her two preschool-age sons Lincoln and Jack what had happened to their father.
An int team of experts hv conclusively confirmed tt the aircraft debris found on Reunion Island is indeed frm MH370 https://t.co/UwRsK1zdA2
"There's been plenty of [sleepless nights], so you know. She's been up for a while though.
"Odds are it will be confirmed but still, what does she tell the boys? A piece of daddy's plane was in the water. It doesn't tell them what happened to him.
"There's a whole part of the story missing and that's what we need to be able to put it to rest for us but also to explain it to these two wee boys."
She said Danica was told the news this morning by a Malaysian official, while other members of the family receiving a transcribed press release about six hours after the news broke.
Her mother has not had any contact from Malaysian officials at all, Ms Weeks said.
She said important questions would remain even if the French prosecutor confirmed the debris' origin, and more wreckage was recovered.
"I don't think it does anything for us at all. We've known it's been missing for 17 months. We know Paul's not with us. All of these people know their family members aren't there. Where are they? We actually want to know what happened.
"You can't get over something like this without understanding firstly, how can you lose a plane? How? I need that explained to me, because it's just absolutely ridiculous. And how can you not know where it went?" she asked.
The plane disappeared on Saturday, March 8 last year.
Among the 239 people on board were Ximin Wang, of Morningside in Auckland, and Mr Weeks, who lived in Perth but came from Canterbury.
Mr Weeks attended Aranui High School in Christchurch before studying at the University of Canterbury.
MH370 left the Malaysian capital Kuala Lumpur for Beijing but never reached its destination.
The plane's disappearance spawned numerous unconfirmed theories and a fruitless search for wreckage in the southeastern Indian Ocean.
On Tuesday, Malaysia asked authorities in islands surrounding Reunion to be vigilant for possible plane wreckage, as France confirmed the object washed up on the Indian Ocean isle was from a Boeing 777.
Transponders and fuselage have still not been found, which meant we did not "know for sure" if the wreckage was from MH370, Fox News reported.
Sea life growing on the flaperon, a wing section, could provide some clues as to the path the plane took during more than 500 days floating in the Indian Ocean, the Washington Post reported.
Malaysian Airline released a statement this morning following the confirmation, offering friends and families "deepest sympathies".
"Malaysia Airlines would like to sincerely convey our deepest sorrow to the families and friends of the passengers onboard Flight MH370 on the news that the flaperon found on Reunion Island on 29 July was indeed from Flight MH370."
The Airline described the discovery as a major breakthrough in resolving the disappearance of MH370.
"We expect and hope that there would be more objects to be found which would be able to help resolve this mystery."
Moving forward, Malaysia Airlines' priority is to continue to provide the latest updates and information to the families and it will fully cooperate with the relevant authorities on the investigation and recovery of this tragic accident.
The Airline said family members of passengers and crew had been informed of the latest developments.
"We extend our deepest sympathies to those affected."
NZ "prepared to help"
New Zealand is prepared to help with any renewed efforts in the search for missing airliner flight MH370, Prime Minister John Key says.
However, the country has not yet been asked, and the type of technology likely to be required for any beefing up of the search is "not in our sweet spot", Mr Key said.
"Historically we have [helped with the search], so we did that early on. The question is whether we have the technology that they actually want and need.
"There's certainly a couple of countries that might have a different type of technology because it's really about looking now at the bottom of the sea floor and very deep ocean, so it's probably not in our sweet spot, but we always stay pretty close to the Australians."
The Australian government had been leading the search, trawling a huge section if the Indian Ocean for the lost Malaysia Airlines flight that went missing 18 months ago.
New Zealand has yet to be asked to rejoin the search for the passenger jet, Mr Key said.
"We haven't been asked, as far as I'm aware, yet to do more," he said speaking to media in West Auckland this afternoon.
"But I did have a discussion with the Australian Deputy Prime Minister [Warren Truss] when I was in the Cook Islands yesterday, and the Australians are running that rescue in that area, and they're actually I think going to double the area that they're searching for MH370.
"I think as a result of finding that debris now in Reunion Island they'll be a lot more confident that they're probably looking broadly in the right place.
"I think for a lot of people it'll be, in a sense, a day of closure - at least they'll probably acknowledge that the plane has crashed.
"But on the other side of the coin it'll be a day of tremendous sadness. These are people who've lost their loved ones, they have no explanation of what happened. Now they'll probably accept that the plane has crashed but I think they'll want much fuller answers as to why it crashed."
'We need to know why'
Jacquita Gomes, the wife of crew member Patrick Gomes, said she was informed by Malaysia Airlines about the news half an hour before Najib's announcement. "Now that they have confirmed it as MH370, I know my husband is no longer of this world but they just can't leave it with this one flaperon. We urge them to continue searching until they find the plane and bring it back," she said.
"We still need to know what happened. They still need to find the plane. They still need to find the black box to get the truth out," she said.
"It brings some sort of closure but not a complete closure. We don't know what happened and where the plane went down. It's not over yet."
Mrs Gomes said she hopes to get her husband's body back so that the family can give him a proper burial and say goodbye. She said she watched the announcement on TV with one of her daughters, while her youngest child, a 15-year-old son, was asleep.
"My son doesn't know yet that his dad is really gone, that he won't be back," she said, in tears. "I will have to tell him tomorrow before he goes to school."
Highly technical efforts to extrapolate the jet's final hours before it would have run out of fuel gave force to the theory that it went down somewhere in the southern Indian Ocean.
No one is certain why the plane deviated so far from its planned route. Analysts have said a close look at the wing part could indicate what kind of stress the plane was under as it made impact. It won't fully solve the mystery of why the plane disappeared, nor will it help pinpoint where the plane crashed.
A six-week air and sea search covering 4.6 million square kilometers (1.8 million square miles) of the southern Indian Ocean surface early last year failed to find any trace of the jet.
The Reunion Island debris would be consistent with the working theory that the jet went down in the Indian Ocean and the debris travelled with the ocean current which moves counter-clockwise.
Malaysian officials, who are leading the investigation into the plane's disappearance, have said the plane's movements were consistent with deliberate actions by someone on the plane, suggesting someone in the cockpit intentionally flew the aircraft off-course.
Since last year, Australian officials who are leading the search effort have operated on the theory that the plane flew on autopilot for hours before running out of fuel and crashing into the ocean. Investigators settled on this scenario after analysing data exchanged between the plane and a satellite, which showed the plane took a straight path across the ocean.
Australian Transport Safety Bureau chief commissioner Martin Dolan said last year that investigators assume the autopilot would have to have been manually switched on, again suggesting that someone in the cockpit deliberately steered the plane off-course.
In defining the search area, the Australian Transport Safety Bureau also operated on the theory that the crew was unresponsive, possibly suffering from oxygen deprivation, as the plane flew on autopilot.
The agency said this was indicated by the loss of radio communications and a long period without any manoeuvring of the plane, though it emphasized this was only a working theory and did not mean that accident investigators led by Malaysia would reach a similar conclusion.
A loss of cabin air pressure could cause oxygen deprivation, or hypoxia, which could make pilots unable to perform even basic tasks.
Some analysts argue that the apparent lack of damage to the piece of wreckage indicates a controlled landing on the ocean, with the jet sinking largely intact.
Another theory is that the jet plunged into the water vertically - high dive-style - snapping off both wings but preserving the fuselage.
Yet another possibility, supported by a flight simulator, is that an out-of-fuel Boeing 777 would belly-flop heavily tail-first, disintegrating on impact.