Airports across Europe scrambled to recover on Sunday after a cyberattack crippled check-in systems, leaving passengers stranded in long queues and forcing widespread cancellations. The attack targeted Collins Aerospace, a US-based supplier of airline check-in and boarding software owned by RTX. The outage disrupted operations at several major hubs, including London’s Heathrow, Berlin Brandenburg, and Brussels Airport. Passengers reported mixed experiences. The latest disruption has sharpened concerns about vulnerabilities in the aviation industry, where reliance on a handful of technology providers leaves airlines and passengers exposed when systems fail.