Crews are cleaning up after high winds and heavy rains passed through Tuesday night. Approximately 350 flights were cancelled, and scores were delayed.
Hundreds of stranded passengers spent the night on cots and were waking up at O'Hare Wednesday. Some of them described scary moments as they scrambled to take cover. One photograph shows hundreds crowding the tunnel between the United Airlines B and C concourses.
O'Hare's control tower also was evacuated briefly.
"They decided to stop the plane and let everybody off. We were rushing through the airport, and I was calling my family and people. And then, we got here and they evacuated more than half of the airport," one passenger said.
After the storms blew through, officials found damage across the airport. The winds were strong enough to move a United Airlines jet parked at a gate. No one was hurt.
The storm also damaged the main parking structure. It took out part of the awning and doors to one of the elevator centers in the sprawling parking lot.
Winds also tore off part of the roof of the Fedex facility at the airport's cargo area.
Lines at Terminal 3 near were moving relatively quickly early Wednesday as airport personnel worked to return operations to normal. Still, the departures and arrivals board indicated more than two dozen American Airlines flights have been cancelled.
ABC7 is told many airlines will issue an update later Wednesday morning.
As of about 3 p.m., ComEd reported 205,000 people across the Chicago area remained without power. The hardest hit areas are in the northern suburbs.