The Airbus A330 operated by Air France stalled during a storm and plunged into the Atlantic Ocean.

The court said even if errors had been committed, a causal link between them and the crash could not be proved.

Families of the victims reacted angrily to the acquittal.

They appeared stunned when the verdict was read out at the end of the lengthy public trial.

Danièle Lamy, the president of the association which represents the victims, said the families were "disgusted" that their long fight for justice had come to nothing.

"All that remains of these 14 years of waiting is despair, dismay and anger," Ms Lamy said.

Claire Durousseau, whose niece died in the crash, said the verdict was a severe blow to those left behind: "Our lost ones have died a second time. I feel sick."

It was the first trial for corporate involuntary manslaughter to be held in France.

Air France and Airbus had always denied the charges, for which they were facing a maximum fine of €225,000 (£200,000; $247,000).

The companies said pilot error was to blame for the crash.

The investigation revealed that the plane had encountered a high-altitude thunderstorm hours after departing from Rio de Janeiro.

When the air-speed sensors froze and gave false readings, the pilots failed to follow correct procedure and lost control of the plane, which plunged into the ocean.

The judge said there had been several acts of negligence by both companies, but that there was not enough certainty to hold Airbus and Air France liable for the crash.

"A probable causal link isn't sufficient to characterise an offence," the judge said in her statement before a packed court room.

Air France expressed "its deepest sympathy" to the relatives and Airbus reaffirmed its "total commitment (...) in terms of aviation safety".

All 12 crew members and 216 passengers on board the flight were killed when the plane crashed into the sea from a height of 38,000ft (11,580m), making it the deadliest incident in French aviation history.

The wreckage of the plane was discovered after a long search of 10,000 sq km (3,860 sq miles) of sea floor.

The victims hailed from 33 different countries.