They are flying till the first accident. Russians always learn on their own mistakes.
Russia has over 30
active volcanoes, so it has enough scientists and experience to monitor current situation.
E.g., here is a couple of excerpts from the latest Kamchatka advisory:
KLYUCHEVSKOY VOLCANO; 56° 03'N, 160° 39'E; Elevation 4,750 m
AVIATION COLOR CODE IS ORANGE
Explosive-effusive eruption of the volcano continues. Ash explosions > 7.0 km (>23,000 ft)ASL could occur at any time. The activity of the volcano could affect international and low-flying aircraft.
SHEVELUCH VOLCANO: 56°38'N, 161°19'E; Elevation 3,283 m, the dome elevation ~2,500 m
AVIATION COLOR CODE IS ORANGE
Explosive-extrusive eruption of the volcano continues. Ash explosions > 10 km (>32,800 ft) ASL could occur at any time. The activity of the volcano could affect international and low-flying aircraft.