From the Web Addendum Vol. I:

Flight: Characters with this ability are naturally able to move through the air, soaring over the battlefield. This allows them to move above any obstacle or scenery feature without any reduction in movement. It can also move freely through impassable features and through other characters, although it can’t end its turn above one. This ability allows it to Charge enemy units without being intercepted by any enemy unit, except for enemy units that also have the ability to fly.