BA is a flag carrier. Russia only allows one airline per European country (and sometimes none) to overfly Siberia. That the government of the UK continues to pick BA as its flag carrier amounts to a state subsidy.
This is something the EU has tried to address in the past, but not much can be done about it as Russia imposes the policy unilaterally.
But regardless of how it started and who's to blame, the net effect is that when BA flies from e.g. London to Tokyo they can pick a shorter route than their competitors, this makes them much more profitable than they otherwise would be. They effectively hold a state-sponsored monopoly on certain routes.
This is something the EU has tried to address in the past, but not much can be done about it as Russia imposes the policy unilaterally.
But regardless of how it started and who's to blame, the net effect is that when BA flies from e.g. London to Tokyo they can pick a shorter route than their competitors, this makes them much more profitable than they otherwise would be. They effectively hold a state-sponsored monopoly on certain routes.