CHICAGO (CBS) — A paperwork mistake caused delays for travelers on Southwest Airlines Wednesday.

Southwest halted flights at Midway International Airport while the issue was fixed. The airline blames a spreadsheet error that occurred during a system update.

READ MORE: Kyle Lowry Scores 19 Points, Heat Beat Bulls 107-104

It caused problems with aircraft weight and balance data.

READ MORE: Chicago Weather: Breezy With A Little More Sunshine

Southwest said it was only a paperwork issue, and not a flight safety issue.

MORE NEWS: 'Success Absolutely Means Survival At This Point': Local Shops Inch Toward Recovery On Small Business Saturday

Also From CBS Chicago: