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US airline Delta says it is ready to re-route services from the US to Asia if Russia imposes a ban on access to its airspace.

The Russian government is considering banning EU and US airlines from crossing its airspace in retaliation for western sanctions over Ukraine.

Delta says that 12 services would be affected if airlines are banned form Siberian airspace.

It is the first airline to publicly announce a contingency plan.

But it is likely that other airlines are also looking at the issue.

In a statement, a spokesman for Delta said: "As a routine matter in running a global airline, Delta continually weighs geopolitical considerations when developing flight plans for the safe and secure aircraft routings of customers and employees.

"Delta is prepared to quickly make alternate routings around closed airspace if necessary, including Russian Siberia."

Shares in airlines were hit on Tuesday when it was first rumoured that Russia was considering a ban on foreign airlines crossing its airspace.