Airborne Units is a third type of units in Age of Mythology and Age of Empires III after land units and ships. Flying units are much more rarely seen, and it is by no means certain any will appear in a given game. The main advantage of flying units is that they are not constrained by any obstacles on the map. They can fly over land, sea, rocks and walls, exploring every corner of the map. Additionally, they can only be attacked by ranged units (including, in some cases, other flying units.)