Case No. 61·United States
2006·Chicago O'Hare International Airport
United States.O'Hare International
On 7 November 2006, at least twelve United Airlines employees watched a stationary metallic disc over Gate C-17 at O'Hare airport before it shot upward, punching a hole through the clouds. The FAA denied holding any records; a Chicago Tribune FOIA suit forced release of the internal audio that contradicted the denial.
Year
2006
Tier
S
Probability
72%
Category
Incident
Strong evidence: instrumental sensor record + multiple witnesses (typically military). Three independent axes: the «tier» measures the strength of the evidence; the «probability» estimates how genuinely unexplained the case is —a natural phenomenon can remain unexplained, so it does not equal «non-prosaic»—; and the partition of explanations (below) says what it most plausibly was. So a well-documented case can have a possible hoax as its most plausible cause, and a Tier B is not, for that reason, a hoax.
Primary documents · viewer

Context · Chicago O'Hare Airport, where United staff saw the disc over gate C17
Concourse B, Chicago O'Hare airport.jpg · Wikimedia Commons · CC BY-SA 4.0 · open original
Part 01
The night in question
On November 7, 2006 around 16:15 local time, ground personnel and pilots from United Airlines at Gate C-17 of Chicago O'Hare airport observed a circular, dark-gray metallic disc-shaped object hovering below the cloud layer at an estimated 500 to 700 meters above the terminal. The object — with no lights, markings or sound — remained stationary for about 5 minutes. It then ascended vertically and abruptly through the cloud layer and, according to several witnesses, briefly left a sharp circular hole in the clouds — roughly 30 meters across — through which blue sky was visible before it closed.
Direct witnesses included at least 12 United Airlines employees: ramp mechanics, operations supervisors, pushback crew and pilots, including at least one who reported the object over internal radio. The crew of United flight 446 to Charlotte, parked at C-17, were among those who saw it. The O'Hare control tower, per the FAA's initial account, had detected nothing on radar and had no records. When Chicago Tribune journalist Jon Hilkevitch put the question to them, both United Airlines and the FAA officially denied any knowledge of the event, and the FAA attributed it to a 'weather phenomenon'.
Hilkevitch filed a detailed FOIA request to the FAA. The documentary pressure forced release of internal communications that contradicted the initial denial: air-traffic-control recordings and transcripts in which a United supervisor asked the tower to confirm whether they could see the object over C-17, proving the report had in fact reached the official system. The January 1, 2007 Tribune article became one of the most-read in the paper's online history. Independently, NARCAP (National Aviation Reporting Center on Anomalous Phenomena), a group of scientists and aviation professionals, conducted a technical investigation led by former NASA researcher Dr. Richard F. Haines and published a roughly 150-page report in March 2007 treating the case as an operational-safety problem, not a matter of belief.
Part 02
Why this case moved the needle
The first post-2001 case where a federal agency (FAA) officially denied a commercial UAP incident and was then forced via FOIA to release internal communications that contradicted its denial. Its probative value lies not in the nature of the object — indeterminate — but in the procedure: it documents that the institutional 'no records' response was a defensive position belied by the agency's own paperwork. The Chicago Tribune coverage marked the return of UAP to mainstream investigative journalism after almost two decades of marginalization, and scientist Richard F. Haines, of NARCAP, framed it as an air-safety problem, not a matter of belief: an unidentified object hovering over a terminal at the busiest airport of its era is, first of all, an unreported operational risk.
Editorial honesty requires presenting the serious meteorological explanation. Astronomer Mark Hammergren, of the Adler Planetarium, noted that the day's atmospheric conditions were favorable for a 'hole-punch cloud' or fallstreak: a hole that forms when supercooled water droplets in a cloud layer crystallize and precipitate out — often triggered by an aircraft passing through the cloud — leaving a circular opening that can persist for minutes. Under this reading, the described 'hole' would be a known phenomenon and the 'disc' a perceptual misinterpretation (pareidolia, scale confusion or reflection) amplified by word-of-mouth among the staff. Proponents reply that the hole appeared exactly where and when the object ascended, that multiple trained observers described a solid, defined object, and that a fallstreak does not explain the preceding five minutes of stationary object. The honest balance: the evidence of the institutional denial-and-rebuttal is solid and verifiable; the nature of the object remains unresolved and admits a non-dismissible conventional hypothesis.
Part 03
What's left on paper
Documented evidence
- FAA O'Hare tower control audio released (November 7, 2006)
- FAA internal traffic control operations logs
- Testimony from United Airlines mechanics and pilots (12+ identified witnesses)
- Jon Hilkevitch article, Chicago Tribune (January 1, 2007)
- FOIA documents released after one year of litigation
Sources
- Hilkevitch, J. — In the Sky! A Bird? A Plane? A... UFO?, Chicago Tribune (1 ene 2007)
- Wikipedia: 2006 O'Hare International Airport UFO sighting
- FAA FOIA Release — November 2006 O'Hare Incident
Patterns it exhibits (2)
Location
Chicago O'Hare International Airport · 41.98°, -87.90°
Distribution of explanations
This case is classified among the model's hypotheses: the bar splits 100% by how much each explanation weighs (the uncertainty is spread across the hypotheses the case supports). Summed across the corpus they produce the comparable partition. It is a different question from the Probability above: that one estimates how likely the case is a genuinely unexplained phenomenon; this one splits which the explanation would be.
Modal hypothesis: Misidentification 70% · sums to 100%
Confused with: No single object identified
Structured analytical judgment, not a calibrated frequency. Forced classification: the mass the evidence cannot assign is spread across the hypotheses the case does support.
Related cases
same country · 2 patterns
USS Jackson — Transmedium Incident (Wiggins, 2023)
2023 · Tier S · 70%
same country · 2 patterns
USS Theodore Roosevelt (Gimbal/GoFast)
2014 · Tier S · 80%
same country · 2 patterns
Mystery Drones · East Coast (New Jersey + NY + bases)
2024 · Tier A · 50%
same country · 2 patterns
Travis Walton (Snowflake)
1975 · Tier A · 50%
Associated actors (1)