I don't think you can at the moment, but Aeroflot is rumoured to be joining the SkyMiles consortium (Delta, AF, etc) imminently, so get the miles on Aeroflot's program and you will be able to use them later for other airlines. If you're really lucky they will go the way of LOT which merged their frequent flier programme into Swiss's Qualiflyer, so after years of thinking I had a bunch of useless LOT miles (which could only be redeemed on LOT) they suddenly turned up in my Qualiflyer account and I was use them to upgrade a Cathay flight, which was something I could never have anticipated when I first flew LOT. (LOT is a good airline by the way, but just a long way from HK or any route I am currently likely to fly)

Whatever you do, don't get on the plane without getting the miles creidted somewhere!