As a ground dude in my day job I take eliminating the air threat seriously and I cringed when I saw the efficiency with which enemy air decimates blufor in Fast Missions. So, I try and whack a couple of fixed wing threats when I can as my first order of business before I go terrorizing redfor ground targets.
At medium difficulty: When aircraft are merging, lock on with Mavericks at max range, loose a couple then get the hell out of the way--I have done it a couple of different ways, either one per target or two, and two seems to get the job done though you can do two at the first target and then one at the second and then see whether you need to send the fourth. How you do it is all a matter of how dextrous you are at locking up targets.
Once the missiles are on their way, root hog or die. So long as you give enemy AI pilots a wide berth they seem perfectly willing to extend professional courtesy your way.
The Maverick is too slow to chase from rear aspect and it's not exactly nimble but provided the target is not offset too much it can manage to put itself in the way of a target unawares. If you're lucky the enemy will not notice the incoming mail. Helicopters are easier and the PK rises accordingly.
Generally, A2A with an A-10 is a losing proposition after the merge. Even the Hog's peers, the SU-25s, are computer controlled and as such have better power management, and certainly better targeting algorithms--I've followed SU17s around and watched them kill Bradleys with 20-30 round bursts at greater than 1Nm. You can't maintain power for a turning fight for long. The helos are tough because they can rotate and tear you apart in short order and they have good countermeasures and aren't shy to use them. Which means you often have to loose air to air missiles at half a mile or less to get it in there, which means exposure to punishment and a need for some luck (created or dumb) for a good release off the rack.
I have found that it's great when you can get an A2A kill but for me it's always the result of somehow making the fight unfair. Which is good business as far as I'm concerned.