Southwest Airlines Co. is working on restoring a normal schedule at Chicago’s Midway Airport on Monday after canceling nearly all flights Sunday because it ran out of de-icing fluid during a snow storm.

The carrier ran through most of a several-day supply of glycol in one day, and couldn’t access additional fluid because of a broken pump on one tank, Brandy King, a spokeswoman, said in an interview. Southwest had to shut down Midway operations at mid-day Sunday, bringing cancellations over the weekend to 250. While a supply of the de-icing liquid arrived early Monday, a “handful of flights” may still be canceled, she said.

“We resumed operations first thing this morning and anticipate being close to normal today,” King said.

Midway, with about 250 daily departures, is Southwest’s largest airport operation. Chicago temperatures dropped to below 20 degrees Fahrenheit Sunday during the storm.