Every twist in the mystery of missing Malaysia Airlines Flight MH370 is painful for the relatives of the 239 people who were on board.

The conclusion last week of French investigators that the piece of an aircraft's wing found washed up on the Indian Ocean island of Reunion in July is indeed from the plane brings back emotions that make moving on difficult.

That it is all that has been found after 18 months of searching provides not answers, but more questions. The agony is likely to end only when there is unequivocal proof of what happened.

A part of a wing does not provide that; it hints at, but does not prove, that the Boeing-777 crashed into the sea.

Only if more substantial wreckage is found will that be confirmed and, so far, a search of 60,000 sq km of the southern Indian Ocean off Western Australia has turned up nothing.

Before the find, there had been talk of scaling back the scouring of the sea bed and pressure within Australia and Malaysia, which are financing the operation, to reduce or even halt funding.

The French prosecutor's announcement gives reason to step up the hunt through re-examining data and keeping a pledge to double the area being scrutinised.

The plane's voice and data recorders hold the key to why it veered off course while on a flight from Kuala Lumpur to Beijing.

Until they are located and decoded, there is no possibility of answering vital questions so necessary for the mostly Chinese relatives to find closure and for airlines and aircraft manufacturers to make changes that could prevent a repeat.

What happened and the location of the plane remain guesswork. The find on Reunion opens new areas of inquiry through analysis of ocean currents.

German scientists have reexamined data and concluded currents carried the wing part to Reunion from south of the Indonesian island of Java, about 3,200 km northeast of the search area.

Every such possibility has to be considered. Malaysia and investigators owe it to those people who have been so tormented by the tragedy.