14 C.F.R. § 93.331
This subpart prescribes special air traffic rules for aircraft operating in the Washington, DC Metropolitan Area. Because identification and control of aircraft is required for reasons of national security, the areas described in this subpart constitute national defense airspace. The purpose of establishing this area is to facilitate the tracking of, and communication with, aircraft to deter persons who would use an aircraft as a weapon, or as a means of delivering weapons, to conduct an attack on persons, property, or buildings in the area. This subpart applies to pilots conducting any type of flight operations in the airspace designated as the Washington, DC Metropolitan Area Special Flight Rules Area (DC SFRA) (as defined in § 93.335 ), which includes the airspace designated as the Washington, DC Metropolitan Area Flight Restricted Zone (DC FRZ) (as defined in § 93.335 ).
14 C.F.R. §93.331