So, is that little bird or attack helicopter annoying you?! Well I have your fix right here!! All you need is the squirrel (Wingsuit lady) And the stinger. Once you have these two things when ever you see an aircraft you wish to destroy throw atleast two grenades at it (Don't worry, these grenades arn't what are going to hurt it at all) Once they are thrown the pilot will see an insta "missile incoming" and will either pop flares instantly. If so it allows you to lock on and insta destroy it rather easily. Now if it didn't pop flares you can actually lock on to it and fire the rocket and it will have no clue that you just shot that rocket!! Because on the pilot side all you hear is the "EEEEEEEEEEEEEEE" of missile incoming from that grenade you just threw.

Thanks for listening to my ted talk

For people who don't like reading (its ok to not like reading)
Wing suit lady
throw tracking grenade at heli
If flares then wait for it to cooldown and shoot with stinger
If no flares shoot with stinger due to the fact its masked by the following grenade