Updated 01/12/12 – 10 p.m.

CHICAGO (CBS) — After cancelling all flights most of Thursday afternoon due to the snowstorm, Southwest Airlines resumed a full flight schedule at Midway International Airport at 6 p.m.

Hundreds of flights were also cancelled at O’Hare International Airport.

Southwest cancelled all flights at Midway between 1 p.m. and 6 p.m. on Thursday as a snowstorm moved across the area. About 100 Southwest flights were affected.

City aviation officials said Southwest resumed its full schedule at 6 p.m.

In all, more than 140 flights had been cancelled at Midway by evening.

“We had a flight at 1:40 that got canceled going to Las Vegas. We tried to get bumped to 11:10. It was full, so we’re going to drive our car to Milwaukee,” one woman said.

One man at Midway said, “I can’t complain with Southwest. This is my first time being canceled.”

At O’Hare, more than 400 flights have been canceled as of 3:30 p.m., and delays of about 20 minutes have been reported for de-icing procedures.

If you’re ticketed to travel Thursday or Friday on most of the major airlines, it’s likely you can get a waiver to change your flight. Travel waivers allow customers to make changes in advance of a storm or other major event, without the fees that would otherwise apply.

Travelers are advised to check their airlines’ Web sites for updates.

The snowstorm is expected to slam Chicago with about 4 to 8 inches Thursday and into early Friday.

(CBS 2′s Kristyn Hartman contributed to this report.)