https://www.cnbc.com/amp/2022/03/14/...ed-planes.html
As mentioned, it appears that Russian airlines will continue to use the planes domestically, and issue their own national [only] flight authorities for the airplanes. The challenge will be that if the airplanes are ever recovered to their western owners, their C of A's will be totally invalid, and the Russian operation outside of the normal C of A authority will render the airworthiness status of the airplanes very unknown. Inspecting and re validating them for western C of A's again will be an immense task, if they're even airworthy at all!