Fragment of plane examined by experts

MH370 vanished more than a year ago with 239 people aboard.

Intact and encrusted with barnacles, the metal piece washed up on the Indian Ocean island of Reunion and was sent to France, where investigators will determine whether it is from the missing Boeing 777, which disappeared after veering far off its set northerly course from Kuala Lumpur in Malaysia to Beijing.

In addition to confirming the provenance of the 777 flap, analysts say the investigators will examine the metal with high-powered microscopes to gain insight into what caused the plane to go down. Malaysian military radar last confirmed the Boeing 777 over the Strait of Malacca.

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.

The French agency that investigates air crashes, known as the BEA, confirmed the inquiry was beginning. Experts from Boeing were also expected in the southern French town.

Analysts have said a close look at the metal of the part known as a “flaperon” could indicate what kind of stress the plane was under as it made impact.

It will not fully solve the mystery of why the plane disappeared, nor will it help pinpoint where the plane crashed.

No other debris from MH370 is known to have washed up in the Indian Ocean.

A six-week air and sea search covering 1.8 million square miles (4.6 million square kilometres) 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.

Authorities are working on a theory that the plane ran out of fuel, but 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.