A cyberattack on Russian state-owned airline Aeroflot disrupted its computer systems on Monday, forcing the cancellation of over 100 flights and delaying many others, Russia’s Prosecutor’s Office said.

Ukrainian hacker group Silent Crow and Belarusian group Belarus Cyber-Partisans claimed responsibility, calling it one of the most damaging cyberattacks since Russia’s full-scale invasion of Ukraine began in 2022.

Aeroflot confirmed system difficulties early Monday, warning of possible disruptions. Crowds of delayed passengers were seen at Moscow’s Sheremetyevo Airport. The outage also affected Aeroflot subsidiaries Rossiya and Pobeda.

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While most cancelled flights were domestic, some international routes to Belarus, Armenia, and Uzbekistan were also hit.

Silent Crow claimed it had accessed Aeroflot's internal network for a year, stealing customer data, employee surveillance records, and internal communications. “These resources are now inaccessible or destroyed,” the group said on Telegram, adding the damage could cost millions to fix.

They also suggested they might soon leak the stolen data, saying, “The personal data of all Russians who have ever flown with Aeroflot have now also gone on a trip — albeit without luggage.”

The Belarus Cyber-Partisans said they aimed to cause serious disruption and had worked for months to exploit vulnerabilities in Aeroflot's systems.

Russia’s Prosecutor’s Office has launched a criminal investigation. Kremlin spokesperson Dmitry Peskov called the attack “quite alarming,” noting that cyber threats remain a serious concern for major service providers.

The incident adds to an already tense summer for Russia’s airports, which have faced multiple disruptions due to Ukrainian drone attacks.