Many Russian planes are registered in Bermuda
As of March 13, 2022, the Bermuda Civil Aviation Authority (BCAA) has provisionally suspended all certificates of airworthiness of Bermuda-registered aircraft operating in Russia. The reason this matters is because roughly half of the commercial jets in Russia are registered in Bermuda (including a majority of the planes that are leased).
International sanctions make it hard for Bermuda to maintain safety oversight of these Russian operated aircraft, meaning that Bermuda can no longer confidently verify that these aircraft are airworthy.
Why are so many planes flying in Russia registered in Bermuda? There are a few reasons, including lower import duties, better safety oversight, and easier and better insurance options. The process of trying to re-register aircraft in Russia is currently taking place, but that also has its complexities.