The universe/setting/novels I'm working on has ten elements, including earth, fire, air, water, lightning, light, shadow, forest, beast, spirit. In my world, all elements can include primary, secondary, tertiary and quaternary effects, and can be modified for use by the ancient powers of chaos, destruction, creation, order, war, wisdom or magic, and can be modified further by the physical, mental, emotional or spiritual.
For example, earth can mean literal earth/stone/sand/rock, or can mean barriers or blockades, or prisons, or a few related things.
Based on that, I think I'd choose air, because I imagine it'd represent physical air, as well as speed and travel.