The workers, some of them pilots, said the object didn't have lights and hovered over an airport terminal before shooting up through the clouds, said a report in Monday's Chicago Tribune newspaper.
The U.S. Federal Aviation Administration acknowledged a United supervisor had called the control tower at O'Hare, asking if anyone had spotted a spinning disc-shaped object. But the controllers didn't see anything and a preliminary check of radar found nothing out of the ordinary, FAA spokeswoman Elizabeth Isham Cory said.
"Our theory on this is that it was a weather phenomenon," Cory said.
"That night was a perfect atmospheric condition in terms of low (cloud) ceiling and a lot of airport lights. When the lights shine up into the clouds, sometimes you can see funny things."
The FAA is not investigating, Cory said.
United spokeswoman Megan McCarthy said company officials don't recall discussing any such incident from Nov. 7.
At least one O'Hare controller, union official Craig Burzych, was amused by it all.
"To fly seven million light years to O'Hare and then have to turn around and go home because your gate was occupied is simply unacceptable," he said.
Copyright © 2007 Canadian Press