Planes are flying again at Chicago's Midway International Airport after a nearly four-hour shutdown caused by a lack of runway lights.

Chicago Aviation Department spokeswoman Karen Pride says a problem with the lighting equipment caused the outage at about 8:30 p.m. Thursday. Pride says 85 flights were canceled or diverted while the airport was closed.

Flights resumed early Friday, and airlines are working to get back on schedule.

The outage didn't affect the terminals, so passengers aboard planes when the runways went dark were returned to the terminals and taken off the planes.

Commonwealth Edison spokeswoman Martha Swaney says the outage wasn't caused by a ComEd power failure, but she says the utility's crews worked with Midway's personnel to help them get their equipment working again.