International Sighting Categorization
(1) The Hynek Classification System
Developed by Dr. J. Allen Hynek, the sightings are divided into distant encounter (DE) (further than 500 ft,) and close encounter (CE) (within 500 ft) sightings.
DE-1 – Nocturnal Light(s) (NL): Well-defined, anomalous light(s) seen in the night sky, whose appearance and/or movement are not explainable in terms of conventional light sources. Most commonly reported.
DE-2 – Daylight Disc(s) (DD): Any anomalous, metallic appearing object(s) seen in the daytime sky, high in the sky, or close to the ground. Can be discoid, or any other shape.
DE-3 – Radar/Visual cases (RV): Objects seen simultaneously on radar and visually by the same or other witnesses. Least frequently reported.
CE-1 – Light/object in close proximity. Strange object(s) or light(s) seen in close proximity (nearby), but without physical interaction with either the witness or the environment.
CE-2 – Physical trace. The UFO leaves physical evidence (such as imprints, soil depression, burns or vegetation damage, physical effects on plants, animals or humans, excessive heating and chemical changes to soil and vegetation), or causes electromagnetic interference (car ignition system failure, damage to electronic gear, lights extinguished etc).
CE-3 – Occupant. Occupants or entities are seen. The occupants may be seen at ‘windows’ of the craft, or on the ground outside the craft. No communication takes place between the witness and the occupant(s).
(Hynek’s classification system has been expanded to incorporate other categories. Along with direct contact with alien beings, these categories also cover abductions or removal of the witnesses from their surroundings, and other reported incidents such as cattle mutilation phenomena. UFO Casebook lists additional categories in which the UFO and its occupants are captured or destroyed by military forces or civilians.)
CE-4 – Communication/interaction. Occupants communicate or interact with the observer(s).
CE-5 – Abduction or boarding craft. Humans or observers are taken onboard the craft.
(2) The Vallee System
Author and researcher Jacques Vallee devised a UFO encounter classification system which is more descriptive than Dr Hynek’s, particularly in terms of the reported behaviour of UFOs.
Type – I (a, b, c, d,) – Observation of an unusual object, spherical, discoid, or of another shape, on or situated close to the ground (tree height or lower), which may be associated with traces – thermal, luminous, or mechanical effects.
a – On or near ground.
b – Near or over body of water.
c – Occupants appear to display interest in witnesses by gestures or luminous signals.
d – 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’.
a – Moving erratically through the sky
b – Object is stationary and gives rise to secondary objects (sometimes referred to as ‘satellite objects’.
c – 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.
a – Hovering between two periods of motion with ‘falling leaf’ descent, up and down, or pendulum motion.
b – Interruption of continuous flight to hover and then continue motion.
c – Alters appearance while hovering – eg. change of luminosity, generation of secondary object etc.
d – ‘Dogfights’ or swarming among several objects.
e – 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.
a – Continuous flight
b – Trajectory affected by nearby conventional aircraft
c – Formation flight
d – Wavy or zig-zag trajectory
Type V – (a, b, c) – Observation of an unusual object of distinct appearance, ie. Appearing to be not fully material or solid in structure.
a – Extended apparent diameter, non-point source luminous objects (‘fuzzy’)
b – Starlike objects (point-source), motionless for extended periods
c – Starlike objects rapidly crossing the sky, possibly with peculiar trajectories