Russia’s national airline Aeroflot was forced to cancel dozens of flights on Monday after a massive cyber attack caused the company’s computer systems to fail. A hacking group called Silent Crow claimed responsibility for the action, alongside an outfit known as Cyber Partisans.

Russia’s flagship airline, Aeroflot, canceled dozens of flights after a cyberattack claimed by the pro-Ukrainian hacking group Silent Crow on the airline’s IT system. Silent Crow said it carried out the attack with the Belarusian group Cyberpartisans.

A cyberattack on Russian state-owned flagship carrier Aeroflot caused a mass outage to the company’s computer systems on Monday, Russia’s prosecutor’s office said, forcing the airline to cancel more than 100 flights and delay others.