It is taking some travellers in Chicago longer to get home for the Thanksgiving holiday.
Dense fog set in over the city forcing hundreds of flights to either be cancelled or delayed.
Both airports that serve the Chicago area, O'Hare and Midway, were affected Wednesday morning.
It was a tricky morning for travellers in parts of southern Ontario and the Maritimes as well.
Thick fog reduced visibility to near zero challenging motorists and causing some bus delays in the region.
With files from CNN