European aerospace giant Airbus has been hit by a series of cyber attacks by hackers who targeted its suppliers for commercial secrets.
There have been four major attacks on Airbus in the past year, according to two security sources involved in investigating the hacking.
The group has long been considered a tempting target because of the cutting-edge technologies that have made it one of the world's biggest commercial plane manufacturers, as well as a strategic military supplier.
In January, the company admitted to a security incident that "resulted in unauthorised access to data", but people with knowledge of the attacks outlined a concerted and far bigger operation over the past year.
According to AFP, the hackers appeared to be interested in technical documents linked to the certification process for different parts of Airbus aircraft.
Several stolen documents were related to the engines of the Airbus military transport plane A400M, which has some of the most powerful propeller engines in the world, said AFP.
The perpetrators of the attacks have not been formally identified.
The incidents reveal the vulnerability of Airbus to intrusions via its global supplier network, and the value of its technology.
There is also an industrial risk for Airbus, with hackers potentially able to knock out production for strategic suppliers which would have a knock-on effect on production.
Romain Bottan of the aerospace security specialist BoostAerospace said the attacks showed that hackers were seeking out weak links in the chain to compromise Airbus's systems.
"The aerospace sector is the one that suffers most from cyberattacks, mostly through spying or people seeking to make money from this industry," said Bottan of BoostAerospace.
"If someone wanted to slow down production, they can quickly identify the critical supplier, the single sources, which are unique in their role," one expert said.