PARIS (AP) — Distraught families whose loved ones died in Air France's worst-ever crash on Monday shouted down the CEOs of the airline and of planemaker Airbus as the two companies went on trial on manslaughter charges for the 2009 accident over the Atlantic Ocean.

Cries of "Shame!" erupted in the courtroom after the executives took the stand.

The crash of storm-tossed Flight 447 en route from Rio de Janeiro to Paris killed all 228 people aboard and had lasting impact on the industry, leading to changes in regulations for airspeed sensors and in how pilots are trained.

The victims came from 33 countries, and families from around the world are among the plaintiffs in the case, fighting for more than a decade to see it come to trial.

"It's very important that we made it to the trial stage. ... Thirteen 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 sign reading: "French Justice. 13 Years Too Late."

The official investigation found that multiple factors contributed to the crash, and the companies deny criminal wrongdoing. The two-month 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.

Airbus CEO Guillaume Faury took the stand on the opening day to say: "I wanted to be present today, first of all to speak of my deep respect and deepest consideration for the victims; loved ones."

"Shame on you!" family members retorted.

"For 13 years you have shown contempt for us!" one shouted.

Air France CEO Anne Rigail met similar emotions when she told the court she was aware of the families' pain.

"Don't talk to us about pain!" rose an angry voice.

The presiding judge called for calm and the proceedings resumed.

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 victims' 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 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 plane's 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 on June 1, 2009.

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 meters).

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 risk. The model in question — a Thales AA pitot — was subsequently banned and replaced.

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

The companies' "image, their reputation" is at stake, said Philippe Linguet, who lost his brother on Flight 447. He expressed hope the trial would expose the failings of Airbus and Air France — two major players in the industry and in the French economy — to the world.

Daniele Lamy, who heads an association of victims' families, said they are bracing for a difficult trial.

"We are going to have to unfortunately relive particularly painful moments," she said. But she called the trial a welcome opportunity after prosecutors initially sought to close the case.

"This will allow the family to express themselves, to express their suffering over 13 years," she said.

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Angela Charlton and Masha Macpherson contributed to this report.