airspace

noun

1. 1

   A specified portion of the atmosphere, especially that under the technical aviation control and/or jurisdiction of a particular state over which territory (and territorial waters) it lies.

   “Various European countries transferred the aviation control of their adjoining airspace to Eurocontrol, while each retaining legal jurisdiction.”

2. 2

   That part of the sky designated for the sole use of aircraft.

3. 3

   Space (i.e. a few neighboring frequencies) available for broadcasting within a particular frequency band.

   “The legalisation of free radios caused a bitter fight for airspace.”

4. 4

   The portion of an enclosed area which contains air, especially breathable air.

5. 5

   The cavity in a cavity wall containing air for insulation.