Close Encounter Classification System

Close Encounter Classification System

The Close Encounter Classification System is a taxonomy used to categorize reported interactions between humans and unidentified flying objects or their occupants. It was originally developed by astronomer and Project Blue Book scientific consultant Dr. J. Allen Hynek in his 1972 book The UFO Experience: A Scientific Inquiry. The system has since been expanded by other researchers.

Original Hynek Classification

Nocturnal Lights

UFO sightings at night that cannot be explained by conventional aircraft or natural phenomena.

Daylight Discs

UFO sightings in daylight, typically oval or disc-shaped objects.

Radar/Visual Cases

Simultaneous radar detection and visual observation of an unidentified object.

Close Encounters of the First Kind (CE1)

A UFO is observed within approximately 150 meters of the witness. No physical interaction occurs.

Close Encounters of the Second Kind (CE2)

A UFO leaves physical evidence — burn marks, radiation, ground impressions, electromagnetic effects on vehicles — or causes physiological effects on witnesses.

Close Encounters of the Third Kind (CE3)

Animated beings or entities are observed in or around a UFO. This category inspired the title of Steven Spielberg's 1977 film Close Encounters of the Third Kind.

Extended Classifications (Post-Hynek)

Close Encounters of the Fourth Kind (CE4)

Proposed by researcher Curt Sutherly and popularized by Budd Hopkins and David Jacobs. Involves abduction of a human by non-human entities. The witness is taken aboard or into a craft and subjected to examinations or procedures.

Close Encounters of the Fifth Kind (CE5)

Proposed by Dr. Steven Greer. Describes bilateral contact — intentional, cooperative communication initiated by humans with extraterrestrial intelligence through meditation, signal transmission, or other methods.

Close Encounters of the Sixth Kind (CE6)

Refers to encounters that cause the death of the witness, an animal, or other living being as a direct result of the UAP event.

Close Encounters of the Seventh Kind (CE7)

Proposed as the creation of human-alien hybrid offspring resulting from a CE4 encounter.

Notable CE2 and CE3 Cases

• Rendlesham Forest (1980) – CE2: ground impressions, radiation readings; CE3 disputed (symbols observed on craft).
• Socorro Incident (1964) – CE2: Police officer Lonnie Zamora observed a landed, oval craft with two small humanoid figures; ground impressions and burned vegetation confirmed.
• Betty and Barney Hill Abduction (1961) – CE4: First widely publicized alien abduction case in the United States; the Hills underwent hypnotic regression and described medical examinations aboard a craft.