This has been national news in Belgium over the past few days.

It seems the company operating check-in services for many airports, Collins Aerospace (no news on their website so far - https://www.collinsaerospace.com/news?#newssearchresults_but...) was hit by a ransomware attack on Friday night, disrupting operations at Brussels Airport, London Heathrow, Berlin and Dublin airports.

Media are reporting that apparently Loki Locker ransomware was used. Check in desks are reverting to pen and paper, and many flights have been cancelled. More disruptions and cancellations are expected tomorrow (Monday September 22nd).