In
Starcraft, the
Air Balance Model was the end result of how
Blizzard Entertainment rationalized giving each race a new air unit in the
Brood War expansion. While the
Protoss Corsair, the
Terran Valkyrie, and the
Zerg Devourer each have the potential to dominate other middle-tech air units (ie. the
Wraith,
Mutalisk, and
Scout), none of the new units have attacks that can hit the ground, and thus, they are
0wnz'd by ground units of any race that can attack air units.
In practice, though, as with many things, the situation falls short of the ideal.
Valkyries seldom sees use by Terran players when compared with the
Wraith, due to the existence of the
Valkyrie sprite bug. The
Corsair has almost completely phased out the
Scout, due to its rapid-fire
splash damage attack and relative inexpensiveness compared with the Scout- and that's not factoring the
Disruption Web ability that the
Corsair possesses. Zerg players seldom make use of
Devourers unless the game runs long, due to the fact that they are very high on the tech tree and are only useful when your opponent goes mass air units, but when held to the Air Balance Model, they are the unit that fits the scheme best of all the new air units.