UFO categorization

Some researchers recommend that observations be classified according to the features of the phenomenon or object that are reported or recorded. Typical categories include:

* Saucer, toy-top, or disk-shaped "craft" without visible or audible propulsion. (day and night)
* Large triangular "craft" or triangular light pattern
* Cigar-shaped "craft" with lighted windows (Meteor fireballs are sometimes reported this way, but are very different phenomena).
* Other: chevrons, equilateral triangles, spheres (usually reported to be shining, glowing at night), domes, diamonds, shapeless black masses, eggs, and cylinders.

Hynek system

Dr. J. Allen Hynek developed another commonly used system of description, dividing sightings into six categories. It first separates sightings based on proximity, arbitrarily using 500 feet as the cutoff point. It then subdivides these into divisions based on viewing conditions or special features. The three distant sighting categories are:

* Nocturnal Lights (NL): Anomalous lights seen in the night sky.
* Daylight Discs (DD): Any anomalous object, generally but not necessarily "discoidal", seen in the distant daytime sky.
* Radar/Visual cases (RV). Objects seen simultaneously by eye and on radar.

The distant classification is useful in terms of evidentiary value, with RV cases usually considered to be the highest because of radar corroboration and NL cases the lowest because of the ease in which lights seen at night are often confused with prosaic phenomena such as meteors, bright stars, or airplanes. RV reports are also fewest in number, while NL are largest.

In addition were three "close encounter" (CE) subcategories, again thought to be higher in evidentiary value, because it includes measurable physical effects and the objects seen up close are less likely to be the result of misperception. As in RV cases, these tend to be relatively rare:

* CE1: Strange objects seen nearby but without physical interaction with the environment.
* CE2: A CE1 case but creating physical evidence or causing electromagnetic interference (see below).
* CE3: CE1 or CE2 cases where "occupants" or entities are seen. (Hence the title of Steven Spielberg's movie, Close Encounters of the Third Kind)


Hynek's CE classification system has since been expanded to include such things as alleged alien abductions (CE4s) and cattle mutilation phenomena.

Vallee system

Jacques Vallee has devised a UFO classification system which is preferred by many UFO investigators over Hynek's system as it is considerably more descriptive than Hynek's, especially in terms of the reported behavior of UFOs.

Type I (a, b, c, d): Observation of an unusual object, spherical discoidal, or of another geometry, on or situated close to the ground (tree height, or lower), which may be associated with traces - thermal, luminous, or mechanical effects.

1. On or near ground.
2. Near or over body of water.
3. Occupants appear to display interest in witnesses by gestures or luminous signals.
4. Object appears to be "scouting" a terrestrial vehicle.

Type II (a, b, c): Observation of an unusual object with vertical cylindrical formation in the sky, associated with a diffuse cloud. This phenomenon has been given various names such as "cloud-cigar" or "cloud-sphere."

1. Moving erratically through the sky.
2. Object is stationary and gives rise to secondary objects (sometimes referred to as "satellite objects").
3. Object is surrounded by secondary objects.

Type III (a, b, c, d, e): Observation of an unusual object of spherical, discoidal or elliptical shape, stationary in the sky.

1. Hovering between two periods of motion with "falling-leaf" descent, up and down, or pendulum motion.
2. Interruption of continuous flight to hover and then continue motion.
3. Alters appearance while hovering - e.g., change of luminosity, generation of secondary object, etc.
4. "Dogfights" or swarming among several objects.
5. Trajectory abruptly altered during continuous flight to fly slowly above a certain area, circle, or suddenly change course.

Type IV (a, b, c, d): Observation of an unusual object in continuous flight.

1. Continuous flight.
2. Trajectory affected by nearby conventional aircraft.
3. Formation flight.
4. Wavy or zig-zag trajectory.

Type V (a, b, c): Observation of an unusual object of indistinct appearance, i.e., appearing to be not fully material or solid in structure.

1. Extended apparent diameter, non-point source luminous objects ("fuzzy").
2. Starlike objects (point source), motionless for extended periods.
3. Starlike objects rapidly crossing the sky, possibly with peculiar trajectories.

Source: 1. Jacques and Janine Vallee: Challenge To Science: The UFO Enigma, LC#66-25843