A ground stop at Midway Airport was briefly in effect.
The issue stemmed from an outage, but Southwest did not immediately disclose the nature of the outage. At about 5 p.m., the issue was resolved, but the major delays continued.
On social media, passengers indicated that they were having trouble with booking flights.
Shortly before 5 p.m., the Midway Airport departure boards showed at least 30 Southwest flights delayed or canceled. At about 4 p.m., crowds filled the Southwest check-in area, but at about 5 p.m. the lines had shrunk significantly. Some passengers have been able to print out there boarding passes.
Flights appeared to be landing at Midway, and some planes were pulling away from departure gate but not immediately taking off.
We are aware and investigating current issues with our systems. We will keep you posted as we have more information to share.— Southwest Airlines (@SouthwestAir) July 20, 2016
If you are seeing this image on the site you are in our waiting room. Don't refresh; we are working hard on a fix. pic.twitter.com/B1IDrDR2aC— Southwest Airlines (@SouthwestAir) July 20, 2016
"Southwest Airlines began experiencing intermittent performance issues earlier this afternoon with multiple technology systems as a result of an outage. We are now managing flight delays across our system, with a temporary ground stop in place for those flights that have not left the gate. We apologize to our Customers whose travel plans are impacted. We have a Team of experts working diligently to resolve the technical issues and their efforts have systems gradually coming back online. We expect to continue our move toward a normal operation but believe it will take time. Updates will be posted on swamedia.com, our Southwest Facebook page and Twitter accounts."