The American aviation authority has grounded all flights at Chicago’s main airport amid dense fog in the region.
The Federal Aviation Administration (FAA) has announced a “ground stop” on flights in and out of Chicago O’Hare international airport, the Midwest city’s main hub.
The grounding order is valid until 8.30am local time (2.30pm GMT).
However once the order lifts, there are expected to be knock-on delays to departures and arrivals.
Earlier today, the FAA ordered a ground stop on flights into Midway international airport, south of Chicago. It has since been lifted.
There is currently a dense fog advisory in place for Chicago and areas around the city until 10am local time.
Flights from O’Hare, the main international hub for Chicago, to Colombus, Ohio; Bloomington, Illinois; and Tampa, Florida were cancelled, while many more were listed as delayed.
Meanwhile at Midway airport, which is south of the city, there were many more cancellations and a handful of flights delayed.
The National Weather Service said there would be “reduced visibility and slippery travel in dense fog” in the areas around Chicago.
“Dense fog will persist through mid morning. Be alert for slippery roads and reduced visibility,” it added in an advisory.
