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More than 100 flights have been cancelled at Denver International Airport after hail damaged about 40 planes and stranded about 1000 passengers overnight.

Airport spokeswoman Laura Coale said on Thursday that all damaged planes had to be evaluated, slowing operations. She says an unknown number of planes have been taken out of service because of damage.

Frontier Airlines says it expects more cancellations on Friday.

The airport was pummelled by three-quarter-inch hail for about 15 minutes on Wednesday night.

Among those stranded at the airport was Wisconsin Governor Scott Walker. He tweeted that he slept on the floor of a conference room after airport staff got him a blanket and pillow.

The airport didn't distribute cots and blankets to all passengers because airlines didn't request help. About 200 people typically spend the night at the airport.