What would happen if Russia closed its airspace to Western airlines?

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An interesting article in the Washington Post looking at the repercussions for airlines if Russia was to ban them from its airspace, as it has started to threaten to do. The worst affected would be Lufthansa, followed by AF-KLM and BA. But would it bankrupt them, as suggested by Russian prime minister Dmitry Medvedev? Unlikely ? and in fact, the loss to Russian airlines, which enjoy overflight fees would also be significant.