It would definitely be annoying for EU airlines, but the EU market is a lot more important for Russian airlines than Russia is for the EU airlines.
For the EU airlines, losing overflight rights would make flights to China, Korea, and Japan about ~20% longer, but it would also mean that they wouldn't have to pay Russian overflight fees, which are about $400 million a year. Not paying these fees offsets some of the additional costs of going around, and Russia loses the overflight fees.
Long haul flights are still subdued due to COVID which means we can play these games at modest cost. However longer term, I think things will normalize wrt airspace including in Belarus.
That Russia can make 400 m in fees means the fuel cost and cost of longer flights going around Russia is worth more.
Yes but perhaps it doesn't matter as much as you'd think to the European airlines. Presumably Russia is charging what the market will bear in overflight fees. If flying over Russia is an option, airlines that choose to go around pay fuel/operational costs for the extra two hours of flying time, but they also must charge less for tickets, because their competitors that overfly Russia get there two hours sooner.
If EU airlines categorically can't overfly Russia, their only economic loss is the extra flying time, not the reduced ticket prices from taking longer, since their competitors are on the same playing field.
The winners in this would presumably be Turkish and the Gulf airlines.
This already happened a couple of days ago. Russia did not approve flight plans for 2 French passenger planes, Germany did the same to two cargo planes, and the matter was resolved by the next day. This also precipitated the need to an EU-wide response on Belarus hijacking a passenger plane.
For the EU airlines, losing overflight rights would make flights to China, Korea, and Japan about ~20% longer, but it would also mean that they wouldn't have to pay Russian overflight fees, which are about $400 million a year. Not paying these fees offsets some of the additional costs of going around, and Russia loses the overflight fees.