Anti-Air Turrets are a Operation Eagle multiplayer-only structure that is able to quickly tear through enemy airships with ease. While they also appear in the Campaign, they're not buildable and exclusively AI-controlled.
The rounds fired by the turret are extremely deadly against air units, they deal splash damage and have a fast firing rate. Avoid getting too close with all types of air units and use ground forces to destroy them. Since Developer's blog 40, these turrets are buildable within the HQ build zone.