[Single Player] The best mission for this is the first campaign mission on Rookie. While controlling the PT boat, move very slowly or not at all and shoot down incoming planes. You can park yourself right under their approach path and take down torpedo bombers in groups of three as they come down to drop their ordnance. Don’t worry about the minisub, the longer it stays alive the more planes you can shoot down. Eventually the other PT boat will sink the sub and you will control Donald’s plane. Shoot down 2-3 of the flights in front of you, and try to avoid being hit by the flak from the ships below. When you see the message on-screen about incoming Zeros, put your throttle to full, get away from the ships, and start circling as tight as you can. The goal is to keep the Zeros alive long enough that you stay piloting the plane for at least 5 minutes. Another flight of allied fighters will eventually come over and shoot them down for you. If you get to 25% health or less, level out and reduce speed to 50% or so, and your allies will make very quick work of the Zeros. You can get this achievement, Air Medal, AA Marksmanship, and Sea Unit Service Medal all at the same time.