Airbus knew of software problems that caused fatal A400M plane crash in May 2015

Accident investigation leak suggests that critical engine management code was accidentally wiped by engineers

Investigators looking into the fatal crash of an Airbus A400M during a test flight in May 2015 believe that Airbus and European safety specialists were aware of the software vulnerability behind the crash.

The Airbus A400M crashed in a field in Seville, Spain when three of its four engines failed following take-off. Four out of six members of crew were killed in the accident.

The plane, intended for military use, relies on data to manage its engines. However, critical code had been accidentally deleted when engineers working for the firm installed additional software before the test flight.

Pilots had no prior warning before take-off - or even during the flight - that there was an issue with the software and only realised when the engines suddenly stopped working.

Following the crash, Spanish military investigators started working on a confidential report to determine the causes of the accident. Completed in the summer, it shows the role Airbus played in causing the crash.

According to extracts seen by Reuters, the engines were affected by faulty software, which the engine manufacturers had apparently warned Airbus and the European Aviation Safety Agency about in October 2014.

They were told that any software fault could render the engines of the A400M useless, and that crew onboard may not receive prior warning when such a problem occurs. That was the scenario, claim the investigators, in the A400M crash in May 2015.

Developed for the militaries of Spain, Britain, Belgium, Germany, France, Turkey and Luxembourg, the project has been plagued with delays and smashed its original, not inconsiderable budget of $23bn. It's been slapped with a plethora of restrictions.

Reuters contacted Airbus to clarify its position on the crash.

It responded by saying that the crash was caused as a result of "multiple, different factors and contributory causes". However, it wouldn't comment on the leaks from the investigation. An Airbus spokesperson said that the company has since reviewed its systems.

"The mitigation measures derived from that report were not sufficient," the investigators wrote in the report.