The discovery of an aeroplane part on the island of Reunion in the Indian Ocean is being investigated to see if it came from missing Malaysia Airlines flight MH370.
The plane disappeared between Kuala Lumpur and Beijing in March 2014 with 239 people on board – no trace has ever been found.
What are the chances this find will solve one of the biggest aviation mysteries ever?
What do we know about the fragment?
The 2m-long (6ft) piece was found by volunteers cleaning a beach in St Andre, on the north-east of the island, on Wednesday.
Initial pictures suggest it is a flaperon – a part of the wing that helps create lift for an aircraft.
Several aviation experts have said it could have come from a large aircraft such as a Boeing 777 – the same model as the MH370 plane.
But all urge caution and Malaysian officials says they want “tangible and irrefutable evidence” before they tell the families of the victims.
How long has it been in the sea?
The fact that the part is quite large could bolster the theory that it has not been in the ocean for long.
Ellis Taylor, an editor with aviation analysis and news company FlightGlobal, told the BBC it was hard to determine the age, as it appears to be made of composite material such as carbon fibre and resin, which can be very hardy and resistant to erosion.
Robin Beaman, a marine geologist with Australia’s James Cook University, said the pictures showed substantial marine growth – gooseneck or stalked barnacles – on the debris. These are commonly found on flotsam in the Indian Ocean, he told the BBC, and only on objects floating on the surface.
Mr Beaman said it was obvious from the barnacle growth that the part had been drifting for “quite a long time”.
But he said it was hard to say how long exactly – it could be years or months – and that it was also unclear how long the part had been onshore before it was found.
How far is it from the search site?
The Australian-led search has focused on a 60,000sq-km area south-west of Perth – Reunion is roughly 6,000km (3,700 miles) west of there.
Though it is a huge distance, it is highly possible that a piece of debris could have travelled that distance in a year, say experts.
“The plane part’s position is consistent with where we think debris might have turned up,” says oceanographer David Griffin of Australia’s national science agency CSIRO.
“Madagascar was probably the highest probability, and Reunion is not far from that in the scheme of things.”
He has computer simulations of the debris path showing the pieces would have initially stayed at the latitude of the search site, before winds and currents – known as the Indian Ocean gyre – pushed them in a north-west arc.
Mr Beaman noted that a boat lost off the Western Australian coast last year was found nearly intact eight months later, west of Madagascar.
If it’s not MH370, what else could it be?
Several aeroplanes have crashed in the Indian Ocean or in the vicinity of Reunion in the past two decades.
Two involved large aircraft which ended up in waters near the Comoros Islands.
One is Yemenia Airways IY626 which crashed in 2009, killing everyone on board except for a teenage girl. The aeroplane was an Airbus 310.
The other is Ethopian Airlines ET961 – the Boeing 767 was hijacked in 1996 and crashed after the engines switched off due to low fuel.
How long will it take to confirm the part’s identity?
Ellis Taylor from FlightGlobal said the identification process would likely take “a couple of days”.
Aeroplane parts, including flaperons, usually come with details such as a serial number, its manufacturer, and safety certification.
Investigators will need to check for the part’s identification details and trace it to the manufacturer, which in turn would have to check its database to see which plane the part was used in.
Could it help us actually find out what happened to MH370?
BBC’s transport correspondent Richard Westcott says if it is part of the plane, although it would confirm the aircraft crashed and broke up, a piece of wing is unlikely to reveal much more about what actually happened on board.
Greg Waldron, of Flightglobal, said what’s really needed are the plane’s flight recorders – one piece alone won’t solve the mystery, he told the BBC.
David Griffin from CSIRO said it would not affect the existing search. “You can’t trace the flight path with enough certainty based on this,” he said.
“All we can say is that the plane part’s location is consistent with our flight calculations, and it won’t affect the seafloor search for MH370.”
Marine salvage expert David Mearns agreed with this assessment. He told the BBC that even if the debris was from MH370, the “uncertainty is too great” to find the crash site given that the plane disappeared 16 months ago.
“I have backtracked wreckage to locate shipwrecks but only over a drift period of one to three days,” he said.
What do the families say?
Jacquita Gonzales, whose husband was a crew member on the plane told the BBC: “A part of me hopes that it is [MH370] so that I could have some closure and bury my husband properly.
“But the other part of me says ‘no, no, no’ because there is still hope. So I’m torn between the two.”
The BBC’s John Sudworth in Beijing says many Chinese families have been reluctant to believe the plane crashed, citing lack of evidence, and there is lingering mistrust about the authorities’ handling of the disaster.
“Every time we get news like this it is like a knife to the heart,” said the mother of one of the passengers.