Flight Sim/Combat games - help?

so i just bought a Saitek X52 for my friend for christmas and i don't know what games he could even get for it. he'll obviously go out and grab the newest flight sim but do thse even have air combat? and if so do they even do it well. i want to get him an air combat game he can mess around with but take advantage of the X52.

thanks in advance.

If he is really, really, really into modern warfare, get him Lock On: Modern Air Combat, as Broken had sugguested. With everything set to realistic, it is a bit of work to get even a basic radar lock and to fire at said locks. However it's full of detail and certainly worth it.