the Russian Government approved a resolution according to which the Russian airlines can provide customers with ticket vouchers instead of money for cancelled flights.
the ruling said that in the event of an emergency, the airlines have the right to unilaterally change the terms of the contract. Document published on web-portal of legal information.
So, the airline may change the date of flight, time instead of the direct route to give the route with a stopover or change the destination at the closest to the original.