At approximately 4:30 p.m on Tuesday November 7, 2006, federal authorities at Chicago O'Hare International Airport received a report that a group of twelve airport employees were witnessing a metallic, saucer-shaped craft hovering over gate C-17.
According to eyewitness reports, the strange object was first spotted by a ramp employee who was "pushing back" United Airlines flight 446 which was departing Chicago for Charlotte, North Carolina. The ramp worker then apprised the flight crew of UA446 of the existence of the spinning, metallic object above their aircraft, and it is believed that both the pilot and co-pilot of this aircraft also witnessed the object at that time.
According to Jon Hilkevitch of the Chicago Tribune in an interview on Fox News' Glenn Beck program: "The disc was visible for approximately two minutes and was seen by close to a dozen United Airlines employees, ranging from pilots to supervisors, who heard chatter on the radio and raced out to view it." The UFO was then seen to suddenly accelerate straight up through the overcast skies. Witnesses reported that the object left behind an open hole of clear air in the cloud layer and that the mysterious hole disappeared or closed within a few minutes. So far, no conclusive photographic evidence of the UFO has surfaced although it was reported to Hilkevitch that one of the United Airlines pilots was in possession of a digital camera at the time of the sighting and may have photographed the event.
Wiki Page
A UFO Casebook editor states that information, dated January 28, 2007, and links to 2 pictures were sent him. Allegedly, the man is an employee who was on duty and saw the UFO at O'Hare on November 7, 2006.
Here is one of them
Chicago Tribune Blog 2010
Chicago Tribune 2010
NPR 1-2007
Witness video a hoax
Alleged O'Hare UFO Photo Reveals Possible ATS Hoax