As you will know American fuel JetA has a generic fuel freeze temperature of minus 40C as opposed to normal JetA1 elsewhere at minus 47C. We have been paying for an ACTUAL fuel freeze analysis of every uplift out of the US for some time and the results have shown that the worst uplift had an ACTUAL fuel freeze temperature of minus 45C so there would appear to be a good margin over the generic freeze limit. Best option would be to top up in Russia: their fuel is ok down to minus 50C!