This is not how the airspace around Chicago normally looks. A fire at a TRACON facility in Elgin, Illinois put a stop to all flights in and out of Chicago's major airports, O'Hare and Midway. Flights are currently experiencing major delays and diversions to other cities.
The Chicago Tribune reports that at 11:30AM local time, employees were evacuated from the facility, and operations were transferred to the facility in Aurora. On LiveATC.net, communications between aircraft and ATC are revealing that some departing planes are getting to their minimum fuel levels and are having to return to the gate. At this time, flights are leaving at a rate of about one every five minutes. You can listen in here. Updates to this story will be made as we know more.
UPDATE 1:15PM CDT: Flights heading to Chicago Midway are being held at their origin cities until 2:00PM CDT. (FAA.gov) Flights heading Eastbound from O'Hare are being held at O'Hare. No departures. (LiveATC.net)
UPDATE 1:40PM CDT: Workers are getting back into the facility where the fire was. Unknown when operations will be back up fully. (LiveATC.net)
UPDATE 2:37PM CDT: The Elgin TRACON facility is still not back up and functioning. ORD is releasing a few flights, but MDW remains on a full stop at this time. (LiveATC.net)
UPDATE 2:59PM CDT: O'Hare has announced that "everyone is released" with 20-mile separation. Ground hold is over.
Screenshots via FlightRadar24