Hynek’s Classification System

J. Allen Hynek developed his classification system as he was working on his book The UFO Experience, to help him organize UFO reports into categories, and also to help him concisely describe UFO reports to the public. The system has been used by CUFOS from its inception and was adopted by many other UFO groups and investigators.

The standard categories include the following.

Nocturnal Lights (NL) – UFOs that appear as only a light, typically round, with no obvious structure. Their appearance and/or motion are not explainable in terms of conventional light sources. The lights appear most often as red, orange, or white. This category is the largest group of UFO reports.

Daylight Discs (DD) – Originally defined as a daytime (daylight) report of an oval or disc-shaped object that did not appear as any conventional aircraft or other known object. It has been broadened to include UFOs that appear as an object, with lights or without, appearing in either day or night, that is unconventional in appearance and/or behavior.

Radar-Visual (RV) – Sightings that include radar detections of UFOs and commonly visual sightings as well, typically by pilots. These reports often involve the military.

There were three types of close encounter categories in Hynek’s system. A fourth was added later.

Close Encounters of the First Kind (CE1) – Sightings where the UFO, whatever its appearance, comes near enough to a witness—typically within about 500 feet—that details of the UFO can be readily observed. There is no interaction with the witness or the environment.

Close Encounters of the Second Kind (CE2) – Sightings where the UFO causes an effect on the environment, or the witnesses or animals. This can vary from marks on the ground, or damaged vegetation, to interference with electronic equipment, vehicles, or mobile phones, to burns or ill heatlh for witnesses. These sightings have been the most important because there was evidence that could be studied after the event.

Close Encounters of the Third Kind (CE3) – Sightings where an entity of some type, whatever the appearance, was seen in or near a UFO. Often the UFO landed, and sometimes there was also an effect on the witness, such as paralysis.

Close Encounters of the Fourth Kind (CE4) – Sightings where a witness reports being taken against their will into a UFO, or at least removed from their normal environment to somewhere else. The witnesses may undergo examinations and sometimes be given information. This category was added in later years to separate abduction reports from Close Encounters of the Third Kind.


Vallée’s Classification System

Jacques Vallée worked with J. Allen Hynek in the pre-CUFOS days and later developed his own classification system. It has not been used nearly as widely but is worth noting because it attempts a more fine-grained and different distinctions than the Hynek system.


Class Name 1 – Sighting 2 – Physical Effect 3 – Beings 4 -Reality Transformation 5 – Injury or death
AN (Anomaly) Amorphous lights, mystery explosions Poltergeist,
materialized objects,
areas of flattened
grass (i.e. crop circles)
Anomalies with
entities (ghosts,
yetis, cryptozoological
beings, elves, spirits)
Near Death Experience
(NDE), religious visions
and miracles, Out Of Body Experience (OOBE)
Anomalous injuries or
death, including
spontaneous combustion and unexplained wounds
FB (Flyby) Continuous trajectory With physical evidence Beings observed Witness sense of reality
change (such as landscape alteration, telepathy, etc.)
Result of fly-by is injury
or death
MA (Maneuvers) discontinuous trajectory With physical evidence Beings observed Witness sense of reality
change (such as landscape alteration, telepathy, etc.)
Result of maneuvers is injury or death
CE (Close encounter) Close approach
(within 500’)
With physical evidence Beings observed Abduction Injury or death