47 CFR § 4.5 - Definitions of outage, special offices and facilities, and 911 special facilities.
(a) Outage is defined as a significant degradation in the ability of an end user to establish and maintain a channel of communications as a result of failure or degradation in the performance of a communications provider's network.
(b) Special offices and facilities are defined as entities enrolled in the Telecommunications Service Priority (TSP) Program at priority Levels 1 and 2, which may include, but are not limited to, major military installations, key government facilities, nuclear power plants, and those airports that are listed as current primary (PR) airports in the FAA's National Plan of Integrated Airports Systems (NPIAS) (as issued at least one calendar year prior to the outage).
(1) Disrupts 50 percent or more of the air traffic control links or other FAA communications links to any airport;
(2) Has caused an Air Route Traffic Control Center (ARTCC) or airport to lose its radar;
(3) Causes a loss of both primary and backup facilities at any ARTCC or airport;
(4) Affects an ARTCC or airport that is deemed important by the FAA as indicated by FAA inquiry to the provider's management personnel; or
(5) Has affected any ARTCC or airport and that has received any media attention of which the communications provider's reporting personnel are aware.
(e) An outage that potentially affects a 911 special facility occurs whenever:
(1) There is a loss of communications to PSAP(s) potentially affecting at least 900,000 user-minutes and: The failure is neither at the PSAP(s) nor on the premises of the PSAP(s); no reroute for all end users was available; and the outage lasts 30 minutes or more; or
(2) There is a loss of 911 call processing capabilities in one or more E-911 tandems/selective routers for at least 30 minutes duration; or
(3) One or more end-office or MSC switches or host/remote clusters is isolated from 911 service for at least 30 minutes and potentially affects at least 900,000 user-minutes; or
(4) There is a loss of ANI/ALI (associated name and location information) and/or a failure of location determination equipment, including Phase II equipment, for at least 30 minutes and potentially affecting at least 900,000 user-minutes (provided that the ANI/ALI or location determination equipment was then currently deployed and in use, and the failure is neither at the PSAP(s) or on the premises of the PSAP(s)).