Again, the article clearly addresses this. What is the incentive for both Southwest management and the Pilot's Union to lie?

“Flight delays and cancellations occurred for a few hours Friday afternoon due to widespread severe weather, military training, and limited staffing in one area of the Jacksonville Air Route Traffic Control Center,”

“The big issue is that Florida is roughly 15% of our trips, but on any given day, upwards of 50% of our aircraft lines flow through Florida,” Jordan told TPG. “You’ve got all those lines that just stopped in Florida, so you’ve got a lot of aircraft caught up in that,”

“We’re not hub and spoke, and we do very little out-and-back,” Jordan said. “So when you stop a line, you’re stopping a line where the aircraft is attempting to flow across the country.”