One Up, Two Down
Holy crap this is killing me. Half of the time they don't fly by where I am. The other half I am getting hammered by the tanks than spawn from the previous alert.
I was level 9 when I started trying for this.
What is the earliest level that they will spawn, and is there a good location on the map to have these come after you where you won't get crushed trying to line up a shot.