A man in his 40s was arrested in West Sussex, England, over a suspected cyberattack that disrupted several European airports, including London Heathrow, Berlin, and Brussels, during the past weekend.

The U.K.’s National Crime Agency said the suspect was released on conditional bail, and the investigation is ongoing.

The attack targeted Collins Aerospace software, which handles check-in, boarding passes, and baggage systems, forcing staff to process passengers manually and causing delays.

While most flights at Heathrow were operating normally by Tuesday, Berlin Airport warned of continued disruptions as specialists worked to restore secure software, CBS News has reported.

European authorities stressed that aviation safety and air traffic control were not affected, though the source of the attack—whether hackers, criminal groups, or state actors—remains unclear.