This rule is unique to flying creatures and it represents the way in which highly mobile flying creatures can be forced to back away from combat by stubborn resistance. The rule only applies to flyers that are capable of flying at the time - if fighting inside a wood or if unable to fly for whatever reason, then flyers are not driven off.

If flyers lose a combat, but pass their Break test and so do not flee, then they are automatically driven off instead. This means they have been beaten away by their foes' stubborn resistance and forced to fly out of their immediate reach. The models are immediately moved 3D6" away from the enemy as if they were fleeing, except that they can turn to face whatever direction they wish at the end of their move.

Driven off models are free to move and fight normally once they have moved. They are not fleeing and other than being driven away from combat suffer no penalties. Although they have been driven off they have not been broken and the enemy does not pursue.