PARIS: Air crash investigators risk being sidelined in a tussle to unlock the secrets of lost flight MH370, fuelling concerns that their role in making flying safer could be diminished.

By drifting on to Reunion Island, the barnacled remains of a Boeing wing part from the Malaysia Airlines jet have given the upper hand to a French judicial investigation, exposing for the second time this year how civil crash investigations struggle to compete with police-led probes.

For decades, reconstructions of disasters by specialist safety investigators have been seen as crucial to making aviation safer, with accident rates at historically low levels.

But in dozens of countries, notably France, they exist in uneasy co-habitation with separate criminal inquiries.

Simmering tensions over the sharing of evidence between civil and judicial investigators came into the open after the crash of a Germanwings jet into the French Alps in March.

They are under scrutiny again after Indian Ocean currents deposited the “flaperon” from the missing Malaysia Airlines flight into the hands of judges investigating the suspected manslaughter of four French citizens out of 239 people on board.

How France handles both cases could have a wider impact given its influence over aviation safety worldwide and the similarity between its civil-law system and most other jurisdictions.

Its BEA safety investigation board is regularly called in to look at incidents because France is home to Airbus, which makes up 42 percent of the world jetliner fleet.

“Criminal investigation should not compromise the important role that air accident investigation plays in keeping flying safe,” said Kevin Hiatt, safety chief at the International Air Transport Association, the trade association for airlines.

Supporters of the French system of parallel investigations say it prevents cover-ups, supports families and benefits from stronger powers of discovery.