Russia’s flagship airline Aeroflot canceled dozens of flights on Monday due to a system malfunction that a hacker group later claimed was the result of a targeted cyberattack.

Aeroflot said it was experiencing disruptions to its electronic systems and had to adjust flight schedules, warning passengers of delays and cancellations.

“Customers may encounter issues when accessing our services,” the airline said in a statement. “We kindly ask passengers to monitor real-time updates on airport websites, information displays, and public announcements across the airline’s route network.”

The airline added that its technical team was “actively working to minimize the impact on flight operations and restore all services to normal as quickly as possible.”