Air vehicles fly through the air. They are usually propelled by air currents, alchemical engines, magic, or in the case of larger air vehicles, a mix of air currents and alchemical engines or magic. Airships, because of their nature, travel though all three dimensions instead of two. When they ascend, they must do so at half their current speed. When air vehicles descend, they can (but do not have to) move at double their current speed. After the ascent or descent, treat the vehicle’s current speed as it was before making the ascent or descent.