CHICAGO - Smoke inside a regional radar facility has forced a halt Tuesday to all incoming and outgoing flights at both of Chicago's airports, shutting down one of the nation's most important aviation crossroads.
The Federal Aviation Administration said in a brief statement that all its personnel were evacuated from the Chicago Terminal Radar Approach Control, or TRACON, facility in suburban Elgin at around 11:30 a.m. CDT.
A ground stop was put in effect for all flights in and out of O'Hare International and Midway airports, FAA spokesman Tony Molinaro said.
Inbound flights already in the air over the area were handled by a backup facility in the city of Aurora.
The FAA says a cause for the smoke has not been determined.
Elgin Fire Capt. Anthony Bailek said the department received a report of smoke in the building around noon.
Most of the smoke was on the second floor, "but they can't find where it's coming from," Bailek told the Chicago Sun-Times.
Aerial TV footage showed a large backup of aircraft lined up along taxiways.
Controllers at the TRACON facility are responsible for managing the region's air traffic as it leaves and approaches all of the area's airports. Once an aircraft is within about 5 miles of an airport, TRACON workers hand over control to that airport's tower.
The Chicago Department of Aviation did not release additional information.
O'Hare airport is the second-busiest in the country and is a major hub. Around half of passengers there are connecting to other flights.
Any disruption to its operations has an enormous ripple effect on the nation's aviation system.
The aviation tracking website FlightAware.com showed O'Hare cancelations mounting to over 300 by about 1 p.m. Disruptions were less severe at Midway.