It depends if you ant to get small kill streaks or bigger ones. For small ones like predator missile, harriers,precision air strike or those kill streaks I would use UAV , Preddy , Harriers.

For bigger kill streaks like kill steaks 9-25.

Pave Low= Preddy- Harriers- Pave Low

AC130 or Sex Child Porn Chopper Gunner- Preddy- Harriers- AC130 or Chopper Gunner

EMP(Shit kill steak)= Harriers- Chopper Gunner or AC130- EMP

Nuke= Same as EMp but instead of EMP nuke. 😀 Comment 🙂