.AAO files are map files used by the game 'America's Army' (AA). 'America's Army' is a series of multi-player shooter games released by the US Army itself, starting in 2002. AAO files will contain a game map. Game maps include such things as terrain, buildings, and other objects. .AAO files are used to create and share custom maps with other game players. .AAO files can generally be found in the 'Maps' directory of the 'America's Army' installation.