The Anti-Air tower is a defensive structure designed to specifically counter flying enemies. As such, they will not target ground creatures.
Anti-Air Towers deal much more damage than Soundbeam Towers, but have a lower rate of attack. Their greatest weakness is the vulnerability to ground attackers; it is practically a sitting duck if it is not protected.
An Anti-Air Tower also provides the ability to use Radar Pulse. This allows a player to see the entire map, including camouflaged and digging creatures, for a short period of time. However, this comes with the cost of 1000 electricity and takes a considerable time to recharge.
In Creature Chaos, the Anti-Air Tower has the ability to unleash an air burst, which damages all creatures in a radius around it. This also costs 1000 electricity and takes a long time to recharge.
In the Campaign, Anti-Air Towers can only be built after Lucy has researched them in Mission 5.