Just tried game booster 3, seemed to make the stock bomber intercept over London quick mission playable for me.I'm not a particularly technical user, but was watching the fps counter and it seemed to improve things especially in less intense missions and free flight.I don't exactly know what's going on under the hood in detail with game booster 3. I don't know, could just be a placebo but seems to improve fps for me.
http://www.iobit.com/gamebooster.html