On Nov. 7, during the late-afternoon rush at Chicago's bustling O'Hare International Airport, something truly astonishing happened. Pilots, managers and mechanics looked up from their ground positions at the United Airlines terminal and saw an odd, disc-shaped object hovering silently overhead, just below the overcast.

Some minutes later, with many eyes now fixated on it, the wingless vehicle shot straight up at an incredible speed and was gone, leaving a crisp hole through the clouds with blue sky visible at the top.

It was definitely not an airplane or any known craft, witnesses said, many of them shaken by what they saw.

"I immediately called our operations center to confirm the sighting and the Federal Aviation Administration was contacted while I drove to the other concourse to talk to the witnesses," a United management employee wrote for a National Unidentified Flying Object Reporting Center investigation.

With the UFO center's input, Chicago Tribune transportation reporter Jon Hilkevitch broke the story in January, which then leapt onto national TV news. "The witness credibility is beyond question," says Hilkevitch, who has spoken to dozens of witnesses.

The FAA and United Airlines initially denied knowing anything about the incident, but taped calls and other evidence revealed their communications about it when it occurred.