A ground stop was issued at O’Hare International Airport at 5:35 a.m. Friday morning due to “snow or ice”, an alert from the Federal Aviation Administration said.

According to officials, no flights will be allowed to enter or leave the airport until at least 8 a.m.

As of 7 a.m. Friday, nearly 1,000 flights were canceled across O’Hare and Midway International Airports, FlyChicago.com reported, with the majority of those cancellations at O’Hare.