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.

Aeroflot canceled 54 of its 260 scheduled flights for the day due to the cyber attack, and an undetermined number of others experienced some amount of delay. 22 outbound flights from Moscow were subsequently canceled the following day,

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.