airspace

or air space (ârˈspāsˌ)

1. The portion of the atmosphere above a particular land area, especially that of a political subdivision such as a nation.
2. a. The space occupied by an aircraft.
   b. A designated sector of space, such as that in the vicinity of an airport.
3. a. Chiefly British Space available for broadcasting within a particular frequency: “Mobile radio has to compete for air space with other services such as broadcast radio, television, and even military services” (Financial Times).
   b. See airtime.