14 CFR 99.9 - Radio requirements.
(a) A person who operates a civil aircraft into an ADIZ must have a functioning two-way radio, and the pilot must maintain a continuous listening watch on the appropriate aeronautical facility's frequency.
(b) No person may operate an aircraft into, within, or whose departure point is within an ADIZ unless -
(1) The person files a DVFR flight plan containing the time and point of ADIZ penetration, and
(2) The aircraft departs within five minutes of the estimated departure time contained in the flight plan.
(c) If the pilot operating an aircraft under DVFR in an ADIZ cannot maintain two-way radio communications, the pilot may proceed, in accordance with original DVFR flight plan, or land as soon as practicable. The pilot must report the radio failure to an appropriate aeronautical facility as soon as possible.
(d) If a pilot operating an aircraft under IFR in an ADIZ cannot maintain two-way radio communications, the pilot must proceed in accordance with § 91.185 of this chapter.