Probabilities

What explains each case

The archive's 375 incidents, each under its most likely explanation. How it is calculated →

How the incidents split

Causa ordinaria probable, sin identificar: 18.4%Aeronave: 18.1%Objeto espacial: 9.9%Objeto astronómico: 9.6%Fenómeno natural: 7.5%Posible fraude: 7.5%Indeterminado: 6.7%Causa psicológica, médica o social: 5.3%Luz o actividad humana: 4.8%Animal: 3.4%Tecnología adversaria: 3.2%No humano: 1.9%Tecnología humana clasificada: 1.6%Fallo de instrumento: 1.6%Relato folclórico o literario: 0.5%18.4%18.1%9.9%9.6%7.5%7.5%6.7%
375cases
  1. Likely ordinary, unidentified18.4% · 69 cases
  2. Aircraft18.1% · 68 cases
  3. Space object9.9% · 37 cases
  4. Astronomical object9.6% · 36 cases
  5. Natural phenomenon7.5% · 28 cases
  6. Possible hoax7.5% · 28 cases
  7. Indeterminate6.7% · 25 cases
  8. Psychological, medical or social cause5.3% · 20 cases
  9. Human light or activity4.8% · 18 cases
  10. Animal3.4% · 13 cases
  11. Adversary technology3.2% · 12 cases
  12. Non-human1.9% · 7 cases
  13. Classified human technology1.6% · 6 cases
  14. Instrument artifact1.6% · 6 cases
  15. Folklore or literary account0.5% · 2 cases

Sum to 100% · 375 incidents

Prosaic 93%7% Anomalous / secret

What lacks an ordinary explanation, decade by decade

0501001940s · 15 casos · heterogeneidad 43%4340s1950s · 50 casos · heterogeneidad 49%50s1960s · 57 casos · heterogeneidad 43%60s1970s · 56 casos · heterogeneidad 45%70s1980s · 33 casos · heterogeneidad 48%80s1990s · 30 casos · heterogeneidad 35%3590s2000s · 21 casos · heterogeneidad 47%00s2010s · 37 casos · heterogeneidad 42%10s2020s · 62 casos · heterogeneidad 53%5320s

Each explanation

Indeterminate

25 cases

The evidence leans toward no explanation.

See the 25 cases

Non-human

7 cases

Non-human intelligence or technology, whether a state controls or hides it or no one does.

See the 7 cases

Aircraft

68 cases

An aircraft: plane, helicopter, drone or balloon (weather, research, party).

  • Airplane19
  • Helicopter2
  • Drone2
  • Balloon20
  • Airborne debris (party balloon, bag, sky lantern)2
  • Source does not pin the object23
See the 68 cases

Likely ordinary, unidentified

69 cases

No source proposes a specific cause, but similar cases that were investigated almost always turned out to be ordinary.

See the 69 cases

Space object

37 cases

A space object: rocket or missile, satellite or reentry —launches, stages and debris reentering, satellite trains.

  • Rocket or missile14
  • Satellite6
  • Reentry7
  • Source does not pin the object10
See the 37 cases

Classified human technology

6 cases

A secret own or allied program.

See the 6 cases

Astronomical object

36 cases

An astronomical object taken for something else: a bright planet (Venus, Jupiter), a star, the Moon or a meteor or fireball.

  • Planet or star18
  • Meteor or fireball12
  • Moon2
  • Comet1
  • Source does not pin the object3
See the 36 cases

Possible hoax

28 cases

Deliberate staging or fabrication.

See the 28 cases

Adversary technology

12 cases

Another state's surveillance technology.

See the 12 cases

Natural phenomenon

28 cases

Atmospheric (plasma, ball lightning, clouds) or optical (mirage, refraction). Meteors and fireballs are counted as astronomical objects.

  • Atmospheric (ball lightning, clouds)11
  • Optical (mirage, refraction, anomalous radar propagation)5
  • Source does not pin the object12
See the 28 cases

Human light or activity

18 cases

A human light or activity (a beacon, a flare or fireworks, a vehicle, an industrial flame or a person) that distance or darkness made look like something else.

  • Beacon or searchlight3
  • Flare or fireworks3
  • Vehicle3
  • Industrial flare1
  • Person2
  • Source does not pin the object6
See the 18 cases

Psychological, medical or social cause

20 cases

Collective contagion, suggestion, sleep paralysis or a medical condition.

  • Collective contagion2
  • Suggestion4
  • Sleep paralysis2
  • Medical or neurological cause3
  • Source does not pin the object9
See the 20 cases

Animal

13 cases

Birds catching the light or insects near the lens, which the camera turns into fast, distant objects.

  • Bird8
  • Insect2
  • Source does not pin the object3
See the 13 cases

Instrument artifact

6 cases

A film defect, a sensor artifact, a false radar echo or a failure blamed on the object.

  • Film or photo defect1
  • Sensor or radar artifact2
  • Equipment failure1
  • Source does not pin the object2
See the 6 cases

Folklore or literary account

2 cases

Legends and period tales with no verifiable witness.

See the 2 cases

Conventional object, not pinned down

0 cases

The analysis points to something ordinary, such as a reflection or a perceptual error, but the evidence does not say what object it was.

Explore the cases in chronological order