PARIS (AP) — Airbus and Air France went on trial on manslaughter charges Monday over the crash of a Rio de Janeiro to Paris flight in 2009 that plunged into the Atlantic amid thunderstorms, killing all 228 people aboard and leading to changes in air safety regulations.

The worst plane crash in Air France history killed people of 33 nationalities, and families from around the world are among the plaintiffs in the case. They fought for more than a decade to see the case come to trial.

“It’s very important that we made it to the trial stage. … 13 years of waiting, it is almost inhuman,” said German Bernd Gans, who lost his daughter Ines in the crash. Another man came to the trial with a cardboard sign reading: “French Justice. 13 Years Too Late.”

Airbus CEO Guillaume Faury and Air France CEO Anne Rigail were among those at the courthouse Monday. Both companies deny criminal wrongdoing, though Air France has already compensated families of those killed.

If convicted, each company faces potential fines of up to 225,000 euros ($219,000), a fraction of their annual revenues. No one risks prison as only the companies are on trial.

Still, the families see the trial itself as important after their long quest for justice, and aviation industry experts see it as significant for learning lessons that could prevent future crashes.

The investigation found multiple factors contributed to the crash of Flight 447. The trial is expected to focus on pilot error, and the icing over of external sensors called pitot tubes.

An Associated Press investigation at the time found that Airbus had known since at least 2002 about problems with the type of pitots used on the jet that crashed, but failed to replace them until after the crash.

The A330-200 plane disappeared from radar over the Atlantic Ocean between Brazil and Senegal with 216 passengers and 12 crew members aboard.

As a storm buffeted the plane, ice disabled the pitot tubes, blocking speed and altitude information. The autopilot disconnected. The crew resumed manual piloting, but with erroneous navigation data. The plane went into an aerodynamic stall, its nose pitched upward and then it plunged into the sea.

It took two years to find the plane and its black box recorders on the ocean floor, at depths of more than 13,000 feet (around 4,000 metres).

Air France is accused of not having implemented training in the event of icing of the pitot probes despite the risks. It has since changed its training manuals and simulations. The company said it would demonstrate in court “that it has not committed a criminal fault at the origin of the accident” and plead for acquittal.

Airbus is accused of having known that the model of pitot tubes on Flight 447 was faulty, and not doing enough to urgently inform airlines and their crews about it and to ensure training to mitigate the resulting risk. The model in question — a Thales AA pitot — was subsequently banned and replaced.

Airbus blamed pilot error, and told investigators that icing over is a problem inherent to all such sensors.