Definition Any airfield that is: Not controlled by ATC in the real world; or Controlled by ATC in the real world, but the current time falls outside of normal airfield/airspace operating times; or Controlled by ATC in the real world, but POSCON ATC is offline.
Any airfield that is:
Definition Airspace that is unstaffed by POSCON ATC.
Airspace that is unstaffed by POSCON ATC.