Bristol Airport has blamed a cyber attack for causing flight display screens to fail for two days.
An airport spokesman said the information screens were taken offline early on Friday to contain an attack similar to so-called "ransomware".
They are now working again at "key locations" including in departures and arrivals, and work is continuing to get the whole site back online.
The spokesman said no "ransom" had been paid to get the systems working again.
Ransomware is a form of malware in which computer viruses threaten to delete files unless a ransom is paid.
Spokesman James Gore said: "We believe there was an online attempt to target part of our administrative systems and that required us to take a number of applications offline as a precautionary measure, including the one that provides our data for flight information screens.
"That was done to contain the problem and avoid any further impact on more critical systems.
"The indications are that this was a speculative attempt rather than targeted attack on Bristol Airport."
Mr Gore said flights were unaffected, but contingency measures and "manual processes", including whiteboards and marker pens, had to be used in place of display screens.
"At no point were any safety or security systems impacted or put at risk."
He said it had taken "longer than people might have expected" to rectify due to a "cautious approach".
"Given the number of safety and security critical systems operating at an airport, we wanted to make sure that the issue with the flight information application that experienced the problem was absolutely resolved before it was put back online."
No flights are understood to have been disrupted as a result.