How to unlock Ghost Pro in Black Ops?

iv completed the other two challenges but the only one i have left to do is to take down 30 aircrafts with a non-kill streak launcher. Iv tried everything but still do no know where i am going wrong. I use a LAW launcher as i find it the easiest. What do i shoot down? I've shot down almost everything, helicopter,chopper gunner and spy plane but still none of them count. what do i have to do? Do i have to take down an aircraft on my first kill? I dont understand the "non-killstreak launcher" part. Please help!!!