Off-duty officers on board handcuffed an unruly passenger after United Flight 2005 diverted from its Chicago-to-Minneapolis route to Dane County Regional Airport in Madison.
Dane County authorities said they were unaware of any injuries or broader public threat, and federal authorities took over the case after the landing.
The Boeing 737-900, configured to carry 179 passengers, had departed O'Hare for Minneapolis before making the unscheduled stop in Wisconsin.
Passengers were forced to deplane in Madison, and United said it was working to get them to their final destination.
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