14 C.F.R. § 99.3
Aeronautical facility means, for the purposes of this subpart, a communications facility where flight plans or position reports are normally filed during flight operations.
Air defense identification zone (ADIZ) means an area of airspace over land or water in which the ready identification, location, and control of all aircraft (except for Department of Defense and law enforcement aircraft) is required in the interest of national security.
Defense area means any airspace of the contiguous United States that is not an ADIZ in which the control of aircraft is required for reasons of national security.
Defense visual flight rules (DVFR) means, for the purposes of this subpart, a flight within an ADIZ conducted by any aircraft (except for Department of Defense and law enforcement aircraft) in accordance with visual flight rules in part 91 of this title.
14 C.F.R. §99.3