I'd use Predator, Attack Helicoptor or Pave Low and EMP and that should net you 15 kills depending on the mode you're playing on. Hardcore matches would be more difficult since most people use Cold Blooded on those maps so TD or Ground War would be more suited for it. Hell, tonight I had a match of Mercenary TD and got a Pave Low and it got me 20 kills by itself.
So definitely use a chopper because using an airstrike or a Stealth Bomber might get you five to six kills if you're lucky and they spawn in the area at the exact time you call it but a chopper will stick around until it's either blown out of the sky or it's 30 seconds are up.
A1C Peck