With more than 70% of flights canceled Wednesday at Midway International Airport, it's unclear when operations will normalize as the air traffic control tower is scrubbed down after coronavirus exposure.
"Midway is open, but operations remain limited," Chicago Department of Aviation Deputy Communications Commissioner Matthew McGrath said.
"We're working with the FAA to resume normal operations as quickly and safely as possible -- which ultimately means having the tower back in service. Given this reality, and for their own business and network reasons, the airlines are making the decision to cancel many flights."
An FAA official said Wednesday afternoon there was no word yet when air traffic controllers could return to the tower.
Authorities closed the air traffic control tower when several technicians tested positive Tuesday for the COVID-19 coronavirus. Passengers are advised to contact their airlines for more information.
On Wednesday morning, Southwest Airlines ceased operations at Midway, but some flights were resuming as of the afternoon.
In all, the Chicago Department of Aviation at 4 p.m. Wednesday reported 378 of 527 flights were canceled in the last 24 hours. Some delays stretched more than 45 minutes.
The department said pilots were following "one-in-one-out" procedures at the airport, which has five runways.
"The air traffic control tower at Midway Airport is temporarily closing while we ensure a safe work environment for air traffic controllers and technicians," the Federal Aviation Administration said Tuesday.
Much of the air traffic in and out of Midway has been handed off to the Chicago Terminal Radar Approach Control facility in Elgin.
TRACON controllers will manage flights until planes are within sight of Midway, then arriving pilots will announce their presence on the airport frequency. Outbound pilots will announce their presence before departing, then be picked up by TRACON staff.