Well right now I'm at the 5th or 6th Mission, the 2nd Mountain pass mission where the Moth flies overhead blowing gusts of wind. So far I've managed to nail it with the rocket launcher which is found conviently enough on this ledge that's almost impossible to land on. Anyway the give you three rockets, so you have limited ammo. The best bet as far as accuracy is to shoot somewhat early go in first person view and then wait on the top of the pass near the entrance to the 2nd stage for it to fly overhead. Shoot it's belly with a rocket a few times and it's dead. Haven't finished the job myself but I've hit it with a couple of rockets on it's stomach and it seems to be working. Good luck!

Alright, after saying what I said before I need to make some corrections, as you walk up the ledges you notice there is a laser gun, the ones for the VSs thats your weapon of choice right there, use it to hit the moth and since it fires and hits very quickly there is no need to predict where the moth will end up next, there should be one dead Moth real soon!

Just killed it with the above strategy that I was talking about, if you don't believe me look at Neogreek's profile!

shoot at the red spots.