Around 3:30 p.m., the FAA said the ground stop was lifted but "limited operations" continued at O'Hare and Midway airports. Hundreds of flight cancellations and even more delays are expected throughout the evening after planes stood for four hours.
At 11:30 a.m., sprinklers activated at the FAA building located at 1100 Bowes Road in Elgin. The motor of a bathroom fan overheated in the women's bathroom, leading to thick smoke- but no fire. Just tracking down the source of the problem took about 45 minutes.
"It was thick enough that our guys felt they had need to 'go on air,' as we call it," Capt. Robb Cagann, Elgin Fire Department, said. "We used our thermal imaging detectors to track heat. And they were able to scan that area and identify that one of the motors was glowing hot."
FAA workers at the Terminal Radar Approach Control (TRACON) building were evacuated, including about 20 controllers who handle air traffic from 5 to 40 miles from the airports.
The controllers were moved to the FAA's Chicago En Route Center in Aurora, and will take some time to acclimate there as TRACON airs out. Normal operations at the Elgin facility resumed around 4:15 p.m.
Delays are expected to continue as airlines play catch-up.
Throughout the afternoon, dozens of planes were backed up on tarmacs at O'Hare and Midway Airports. Some returned to their gates. Others stood still. A few were allowed to take off during "limited arrivals and departures," according to the Chicago Department of Aviation.
More than 600 flights were canceled and most others were delayed at least an hour at O'Hare Airport. At Midway, about 75 flights were canceled and there were reports of significant delays.
Nora Ten Broeck sat on a plane at O'Hare for several hours. She's headed to Baltimore from Chicago.
"The only info we passengers got was there was an emergency evacuation of a regional center and there was no one in the building," she said.
Her flight was eventually canceled and she was put on another flight. That, too, was canceled.
"At least I wasn't on an incoming plane," she said.
David Wetherelt was flying on an incoming plane from San Diego to Midway when his Southwest Airlines flight was placed in a holding pattern for half an hour before being diverted to St. Louis along with several other planes.