Flying heroes have the "flyer badge" in their stats window. The flying heroes are: Old Curse, Poisoned One, Master Mage, Phoenix, Pilot, Witch, and Griffin If you lack flying heroes, you can go for "Difficulty II" - Kills with Commando, 2 ranged heroes, one tank, and one flying hero. With the speed Buff from Commando there should be enough damage to kill him with one flying hero. As long as you dont have 5 flying heroes, take one tank so that your flying heroes survive longer ( such as Iron Hoof, Dwarf Warrior or War Chief).