Hey, subs feel a lot safer than slow-firing rifles, or even an MG with huge recoil.
CoD is a huge mix of meelee, sniping, short/long range burst fire, etc, etc. Makes it difficult to select your weapon correctly. I like a mix of any SMG and a Sniper. Preferbly those that reload FAST.
Back to topic, though. I don't really think that's possible, seeing as how the planes will be moving like Mach 0.8-M 1.3 something? Apart from that, the altitude will just freeze you before you manage your first burst of bullets. And, apart from that, low alt is impossible, or you might find the ground scores the most kills on that day.