A NMAC is an incident associated with the operation of an aircraft in which a possibility of a collision occurs
as a result of proximity of less than 500 feet to another aircraft, or a report is received from a pilot or flight
crew member stating that a collision hazard existed between two or more aircraft. A report does not necessarily involve
the violation of regulations or error by the air traffic control system, nor does it necessarily represent an unsafe
Historically, a NMAC was classified as an incident and reports of NMAC events were maintained in the FAA's Incident Data
System, together with reports of a variety of other events. By the mid-1980's, NMAC's were considered to be sufficiently
important to warrant the establishment of a separate reporting system and investigative procedures. All NMAC reports are
thoroughly investigated by FAA inspectors in coordination with air traffic controllers. Data obtained from NMAC reports is
used to develop programs, policies and procedures to reduce NMAC occurrences and thereby enhance the safety and efficiency
of the air transportation system.
It is the responsibility of pilots and/or flight crew members to determine whether a NMAC actually did occur and, if so, to
initiate a NMAC report. There is, however, no regulatory or legal requirement that a pilot and/or flight crew report a NMAC
event, although they are encouraged to do so. The fact that pilots and/or crew members initiate NMAC reports raises two
important issues for the user of this information. First, to some degree the data likely will be subjective. This
necessitates that considerable caution be exercised when evaluating individual NMAC reports. Second, the number of
NMAC reports filed probably will not represent the total universe of such events. Therefore, the use of this data to
calculate NMAC rates by individual airline is unlikely to result in a metric that is a valid indicator of safety
Using the Database
Things You Should Know
The NMAC reporting system was revised substantially in 1992. Only reports submitted since that revision are available on
this Web site. The geographic location of a NMAC is reported in terms of distance (nautical miles) and direction
(degrees magnetic) from the nearest air navigation facility, airport or airway fix
(VOR, NDB, airport, airway intersection). Those that occur in oceanic airspace are reported by latitude and longitude.
Since several air navigation facilities frequently are located adjacent to airports, selection of an airport in the search
criteria is unlikely to result in the retrieval of all reports that otherwise could be associated with that airport.
The data received in a NMAC report represents what the reporter believes he/she saw or experienced. The accuracy of the
reporting individual's perception of what occurred can vary considerably among the pilot/flight crew population, depending
upon a variety of factors such as pilot/flight crew experience, visibility conditions, proximity of the aircraft involved,
relative angle of approach, size of the aircraft involved, the trauma experienced by the pilot or flight crew, etc.
For example, at higher altitudes, in the absence of visual reference points, even the most highly trained and experienced
pilots may experience difficulty when reporting such critical information as missed distance, particularly when the NMAC
encounter may have lasted only a fraction of a second. While one of the purposes of the subsequent FAA investigation of a
NMAC report is to remove as much subjectivity as possible through verification of the information contained in the
pilot/crew member report, the investigator's ability to verify this information may be very limited;
e.g., if the location of the NMAC event is outside air traffic control radar coverage, precise verification of missed
distances is a formidable task.
The submission of a report of a NMAC event can be influenced by many considerations. Pilot experience and the operational
environment they routinely fly in can influence reporting. Pilots that routinely fly in heavily used airspace and are
familiar with operating in relatively close proximity to other aircraft may consider an encounter of this type to simply be
a part of the operational environment and not something that merits reporting, whereas a pilot that usually flies in
sparsely used airspace and is unfamiliar with operating in close proximity to other aircraft may consider the same event
to be an extremely serious event that urgently must be reported.
Past reporting trends also suggest that the motivation to report is at least in part influenced by pilot perception that
the reporting of NMAC events contributes to aviation safety and therefore is worth the time and effort required to file a
report. Following a NMAC event that receives widespread media attention, there is a tendency for the number of reports
filed initially to increase, sometimes substantially, and then to decline over time to near previous levels. Fear of a
potential FAA penalty or even attitudes that pilots and flight crews hold about governmental institutions can influence a
decision whether to file a NMAC report.
Some NMACs, including those which may involve unsafe conditions, may not be reported either because of lack of awareness
of the NMAC reporting system or the fact that the flight crew simply did not see the other aircraft due to restricted
visibility. The cumulative effect of all these factors that influence the submission of a report is that it is highly
unlikely the NMACs reported to the FAA represent the total universe of these events.
Types of Search
Textual search across all data fields is provided. Identifying additional information prior to the search can also narrow
the search: Report Number, Start/End Dates, State Code, Aircraft Make/Model, Operator/Airline, Type of Flight Operation and
Airport Identifier. In general, keyword searches using just the text search box will not return the same number of records
as searches conducted using the additional fields on the query screen. This result is because the text search box searches
for all occurrences of a word or string throughout the report, whereas a field on the search form is tied to a single field
on the report. The "Help" function on the query screen provides examples of how to structure queries.