There are multiple ground AAs in the air maps, normally fixed turrets in the deployment bases and an annoying AA vehicle.

I have become quite proficient at avoiding AA and helicopter fire now, using guided missiles and ECM jammer really helps as a pilot and stealth/guided/flares or thermal as passenger in choppers is good, not so good with jets, however i dont do to bad with the B2K jets they are good when hovering close to enemies and using the downward pointing lock on ground missiles

On the PS3 there is only one AA on conquest maps and that is on Wake