A power outage darkened the north end of O’Hare’s airfield Thursday night, affecting four of the airports seven main runways.
The FAA reported lights were out or flickering about 9:20 pm.
The problem was fixed by 10 p.m.
Fortunately, air traffic at O’Hare slows down by that hour, so relatively few flights were affected.
The aviation department is still trying to determine the cause.
Rain and fog were already causing 90 minute delays throughout the day.