The Paris prosecutor has confirmed that the aircraft wing piece found on Reunion island in the Indian Ocean is from the missing Malaysia Airlines flight MH370.

Malaysia’s prime minister, Najib Razak, said in August that he had confirmation that the flaperon discovered on Reunion’s Saint-André beach in July was from the missing plane, but the French authorities were, until this week, more cautious about identifying the debris.

In a statement issued from his office on Thursday, Paris prosecutor François Molins said, however, that analysis of the flaperon had allowed investigators to determine “with certitude” that it came from Flight MH370, which disappeared on March 8, 2014, with 239 people on board. The plane was en route from Kuala Lumpur to Beijing.

A technician at Airbus Defense and Space in Seville, Spain, was able to confirm to investigators that a number inside the wing piece corresponds to the MH370 flaperon serial number.  The Seville-based company supplied the flaperon to Boeing, who built the 777.

After initial analyses, carried out at the Direction générale de l’armement (General Directorate for Armament) near Toulouse, investigators said they hadn’t been able to find any unique identifying numbers to establish an irrefutable connection to MH370.

However, further investigation using a borescope enabled them to find three numbers inside the flaperon and it is one of those numbers, the investigators say, that indicates that the wing piece is from the missing plane.

If the flaperon washed up on the French-governed island is indeed from MH370 it is the first piece of physical evidence that has been found in the massive international search for the plane. Despite the biggest air and sea search ever carried out – involving 65 aircraft and 95 vessels – and detailed examination of a huge area of the ocean floor, no other debris has been discovered.

Malaysia’s transport minister Liow Tiong Lai said that the latest findings dispelled any doubt about whether or not the flaperon was from Flight MH370. He said the strategic working group, which involves Malaysia, China, and Australia, would act to intensify the search for the missing plane.

The search for MH370 has been centred on an area of the southern Indian Ocean about 2,000 kilometres off the western coast of Australia, but there are many who have cast doubt on the calculations by the British company Inmarsat that determined the search location.

Investigators reached their conclusion that Flight MH370 ended in the southern Indian Ocean on the basis of Inmarsat’s analysis of satellite pings – or handshakes – from the aircraft.

Malaysia’s former prime minister, Mahathir Mohamad, says that the fate of the plane has been concealed.

Fate of MH370 is still a mystery

While the identification of the flaperon is an extremely significant development, the mystery of what actually happened to Flight MH370 remains unsolved and relatives and friends of those on board the missing plane are still a long way from finding real closure.

However, some theories – such as the suggestion that the plane landed at the Yubileyniy airstrip in Kazakhstan – may now finally be discarded.

There are those that say the aircraft was shot down by the United States military when it was en route to Diego Garcia, an atoll in the Indian Ocean that is owned by the British and is home to a major US military base.

This is a theory that has been put forward by the former director of the French airline Proteus, Marc Dugain. He has suggested that US military personnel may have shot down MH370 over the Indian Ocean to prevent it being used to attack the Diego Garcia base.

Dugain also speculated that the plane may have been forced to divert from its flight path because of remote hacking or an on-board fire.

He pointed to the testimony of residents of the Maldives who said they saw an airliner travelling towards Diego Garcia on March 8, but whose claims were dismissed.

Despite the discovery of the flaperon, it would still be extremely difficult for investigators to work out where the main wreckage of MH370 is located. Indian Ocean currents can carry debris for thousands of kilometres and drift modelling is known to be imprecise.

The chief commissioner of Australia’s transport safety bureau, Martin Dolan, said in August that the discovery of debris would not help pinpoint where the plane went down. He told the Agence France Presse (AFP) news agency: “Over the last 16 or 17 months, any floating debris would have dispersed quite markedly across the Indian Ocean.”

Australia’s federal transport minister, Warren Truss, said that reverse modelling of ocean currents to determine where Flight MH370 went down was “almost impossible”.

Interim report

A 584-page interim report on the findings of the international safety investigation team, which was released in March this year, reveals that the battery on the beacon of the flight data recorder expired more than a year before MH370 vanished.

The report, which was released to comply with International Civil Aviation Organisation requirements, contains extremely detailed technical information, but gives no clue as to what might have happened to the Boeing 777.

The report confirms that the last transmission from the Aircraft Communication Addressing and Reporting System (ACARS) on MH370 was made at 0107:29 Malaysian time, 25 minutes after take-off. The Malaysian authorities say the ACARS and transponder were deliberately turned off.

Malaysian statements

Najib Razak said in August: “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 onboard MH370. They have our deepest sympathy and prayers.”

Najib said after the disappearance of MH370 that there was a “high degree of certainty” that someone on board the aircraft deliberately disabled the ACARS, which transmits information about an plane’s engine health, and had also switched off the transponder, which transmits such details as altitude, speed, and location.

The prime minister said at that time that MH370’s movements were “consistent with deliberate action by someone on the plane”. The plane did turn around after take-off, and flew on well after its apparent disappearance, he said.

In January, the director-general of Malaysia’s Department of Civil Aviation, Azharuddin Abdul Rahman, officially declared the disappearance of Flight MH370 to be an accident and said that all 239 passengers and crew on board were presumed to have died.

He said the underwater search in the southern Indian Ocean was continuing, but after 327 days, and based on available data, survivability in the defined area was “highly unlikely”.