Checkpoint 1: Try to get between 15 and 20 kills before you land (it helps greatly pressing both the RB and RT buttons so you fire your cannons at the same time. Also make sure you look down the sight (LT)).
Checkpoint 2: Next you want to get 25 kills, you should have this by the time you switch from the second gun (first is the front of the plane, second is the right side i think).
Checkpoint 3: Next you want to get 35 kills by the time you leave the third gun (this is the one that took me the most attempts).
Checkpoint 4: Now you move back to the front gun and should have no problems getting the last 10 kills (again, use both cannons and machine gun fire whenever your using the front gun).
*also when you get a chance destroy the PT boats, it seemed to result in more zeroes.
*the number of kills are the bare minimum, if you dont have at least that many i would strongly suggest restarting the checkpoint.