(AFP) - A Paris court will on Monday hand down its verdict in the trial of Air France and plane manufacturer Airbus over the 2009 crash of a Rio-Paris flight, with families of the victims hoping judges will ignore the recommendation of prosecutors not to seek a conviction.

Prosecutors said as hearings in the eight-week trial wound up in December it was "impossible" to convict the two aviation giants, which have been charged with involuntary manslaughter but deny the charges.

The two France-based companies went on trial in October to determine their responsibility for the worst aviation disaster in Air France's history, which left 228 dead on board flight AF447.

If convicted when the decision is read out from 1130 GMT, the two companies risk only a fine of 225,000 euros ($250,000) but the reputational symbolism is important.

Victims' families were enraged by the prosectors' recommendation.

Daniele Lamy, president of the association which represents the victims said the families did not accept the recommendation, saying it essentially found against the pilots and not the companies.

"What we hope, what we expect, is that the court finally pronounces an impartial decision and condemns Airbus and Air France, who are guilty of the negligence and failures," she said.

"This is what we have fought for over almost 14 years."

The relatives have a "confident expectation" and a "desire for justice", said Sebastien Busy, one of their lawyers.

They "hope that the court will have heard our arguments, that we will have an explanation of the causes and a determination of responsibility".

Throughout the trial, representatives of Airbus and Air France maintained the companies were not guilty of criminal wrongdoing.

Their lawyers demanded acquittal, describing this as a "difficult decision from a human point of view, but technically and legally justified".

- 'Lost our speeds' -

The prosecutors' decision not to seek a conviction does not mean that the three-person team of judges overseeing the trial has to follow their advice.

Prosecutors initially dropped charges against the companies in 2019 in a decision that also infuriated victims' families.

A Paris appeals court overturned this decision in 2021 and ordered the trial to go ahead.

At the heart of hearings in Paris has been the role of defective so-called Pitot tubes, which are used to measure the flight speed of aircraft.

The court heard how a malfunction with the tubes, which became blocked with ice crystals during a mid-Atlantic storm, caused alarms to sound in the cockpit of the Airbus A330 and the autopilot system to switch off.

Technical experts highlighted how, after the instrument failure, the pilots put the plane into a climb that caused the aircraft to lose upward lift from the air moving under its wings, thus losing altitude.

"For us, what led the crew to react in the way they did remains a mystery in most respects," Air France representative Pascal Weil, a former test pilot, told the court on November 10.

Airbus has also blamed pilot error as the main cause for the crash during proceedings.

But lawyers for the families have emphasised how both companies were aware of the Pitot tube problem before the crash, and that the pilots were not trained to deal with a high-altitude emergency of this nature.

The model of Pitot tube used on the doomed Airbus plane, manufactured by French company Thales, was replaced on aircraft worldwide after the accident.

The crash also prompted an overhaul of training protocols across the industry, in particular to prepare pilots to handle the intense stress of unforeseen circumstances.

On October 17, lawyers and victims' families were allowed to listen to the chilling in-flight voice recording of the pilots' final minutes for the first time.

"We've lost our speeds," one pilot is heard saying before a recorded warning sounds -- "stall, stall, stall" -- and the aircraft begins to plunge towards the Atlantic Ocean.

It took nearly two years to recover the "black box" flight recorders which were found nearly 4,000 metres (13,000 feet) below sea level.

© Agence France-Presse