1. a space occupied by air.
2. the amount of breathing air in a room or other enclosed space.
3. the region of the atmosphere above a municipality, state, or nation, over which it has jurisdiction.
4. the region of the atmosphere above a plot of ground, to which the owner has rights or access. Also,air'space" (for defs. 3, 4).
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.