Malware could have played a significant part in the horrific 2008 Madrid air disaster that left 154 people dead, according to a Spanish newspaper.
An internal report by the plane's airline, Spanair, discovered a central computer which registered technical problems was not functioning correctly due to an infection, El Pais said.
This meant technical problems with the aircraft had not been picked up, the report claimed.
Other problems, which would not have been due to malware contamination, also went unnoticed, such as the plane taking off with its flaps and slats retracted.
However, if the Trojan infection had not been present, the flight may never have attempted to take off in the first place and the tragedy could have been avoided, the report suggested.
"We cannot confirm whether malware played a part, nor do we know which particular malware it could have been," Mikko Hypponen, F-Secure chief research officer, said.
"However, over the years, we have seen real-world infrastructure affected by computer problems. In most cases, this has been just a side effect; the malware behind the problem wasn't trying to take systems down, it just did," he added in a blog post.
Malware, if it was present in the airline systems, was likely to have just been a contributory factor that led to the tragedy, not the main cause, according to Sophos senior technology consultant Graham Cluley said.
"It's very probable that there will be found to be other contributing factors to what was a horrific accident beyond the malware infection by Trojan horses," Cluley added in a blog.
"However, next time someone tries to convince you that the people who write malware aren't really doing anyone any serious harm - remember this case."
The final report from crash investigators is due to be presented in December.
