A unit will move on air and ignore all terrain. Itcannot be attacked by close combat ground or water units and its immune to Stink Cloud. Although, it is vulnerable against Anti-Air Towers and ranged units. Soundbeam Towers are weak upon this units. When equipped with this ability, units will turn to Research Level III automatically.
All birds and some insects have this ability. The Bat is the only rodent with it. Flight can only be given to a unit by the Wings of the respective animal.
Due to the weakness of Soundbeam Towers against this units, it can be used to destroy this structures to clear the way for ground units to enter the enemy base.
If you reach Research Level III before your enemy does, you have an advantage upon them due to the fact they are not allowed yet to build an Air Chamber and so cannot build units with Flight.