Aviation experts say it is likely that a large object that washed up on the shore of Reunion, a French island in the Indian Ocean, is wreckage from the missing Malaysia Airlines Flight MH370 that vanished more than a year ago.

In the information vacuum that surrounded the plane's disappearance in March 2014, speculation and theories abounded about what might have happened to the aircraft and all 239 people who were on board when it dropped off the radar.

Those theories ranged from the seemingly plausible, to the downright farcical.

In light of the potential breakthrough, we revisit the theories proposed at the time by experts and online sleuths to see whether their ideas could still hold true.

1. The plane was hijacked and flown to an airport in Kazakhstan. FALSE

Jeff Wise, a science journalist and author who researched the disappearance of MH370, released an e-book this year outlining his theory that the plane was hijacked on Russian President Vladimir Putin's instruction and flown to an airport in Kazakhstan.

Wise argued that the flight's data could have been tampered with by hijackers, and claimed to have found a place where the plane could have landed - an airstrip called Yubileyniy, part of the Baikonur Cosmodrome.

Some who examined Wise's hypothesis regarded it as fanciful - which would seem an accurate assessment if the wreckage found overnight is confirmed as coming from MH370.

2 - Pilot suicide. POSSIBLE

While no evidence has emerged that the captain of the MH370, Zaharie Ahmad Shah or co-pilot Fariq Abdul Hamid died by suicide, the idea has been included in possible theories.

At least seven fatal incidents are believed to have been intentionally caused by pilots since 1982, including the Germanwings loss, which investigators believe happened when co-pilot Andreas Lubitz crashed the Airbus A320 after locking his captain out of the cockpit. Lubitz was later found to have been mentally unstable and undergoing medical treatment for depression.

3 - A catastrophic mechanical failure occurred - POSSIBLE

Some have suggested that there was a catastrophic mechanical failure on board the plane, causing it to disintegrate in mid-flight.

"The fact that we are unable to find any debris so far appears to indicate that the aircraft is likely to have disintegrated at around 35,000 feet," a source involved in the investigations in Malaysia said at the time.

However, one aviation expert told the South China Morning Post at the time that it was mysterious that even if the plane had disintegrated, debris had not been detected on air traffic control radar.

The theory echoes the 2009 Air France tragedy when the plane disappeared over the Atlantic after it flew into turbulence en route to Paris.

It took five days for rescue teams to find the first bits of wreckage and another two years to find the bulk of the destroyed plane.

4 - The plane was shot down in a military exercise. UNLIKELY

One theory suggested the plane was accidentally shot down during a joint US-Thai military exercise in the South China Sea. It was proposed in a book called Flight MH370: The Mystery, by Nigel Cawthorne.

"The drill was to involve mock warfare on land, in water and in the air, and would include live-fire exercises," Cawthorne wrote in his book.

However, the wreckage that washed up overnight was thousands of kilometres away.

5 - Plane was shot down while heading to US military base

In December, Marc Dugain, the former head of a French regional airline, suggested the plane had been shot down by the US because it was heading towards its military base on the island of Diego Garcia in the Indian Ocean.

Reunion and Diego Garcia are about 2400 kilometres apart in the Indian Ocean, but there is no evidence to suggest this theory is correct.

6 - Terrorist hijacking - POSSIBLE

The plane turned wildly off course, its communications systems were "deliberately" disconnected and it carried on flying south over the Indian Ocean on the day it disappeared, leading some to speculate that the plane had been hijacked.

Authorities have found no motive nor any evidence to say definitively that the plane was hijacked.

7 - Plane caught on fire soon after take off - UNLIKELY

New Zealander Mike McKay had been working on the Songa Mercur oil rig in the South China Sea when he saw an "orange light" in the sky on the day MH370 disappeared.

His initial statement described what he believed to be an aircraft on fire at a high altitude.

The fire burned itself out in about 10 to 15 seconds and he gave an exact location based on his position on the oil rig platform.

However, his sighting could be discounted due to the distance from Reunion, where the wreckage washed up.