Windows 3.1, launched in 1992, is likely not getting any updates. So, when CrowdStrike pushed the faulty update to all its customers, Southwest wasn’t affected (because it didn’t receive an update to begin with).
Aside from Windows 3.1, Southwest also uses Windows 95 for its staff scheduling system.
One X user suggested that the company switch to Windows XP—it’s also no longer updated, and it can run Windows 3.1 applications via compatibility mode.
I couldn’t find any sources either. In 2022, they had issues that were attributed to aging technology and reluctance to go digital on their processes, but nothing to suggest Windows 3.1
The was a quote from a union rep that said their programs “looked like they were designed on Windows 95”.