Isn't this hacker news? Weather happened, now lots of planes and flight crews are not at airports they are supposed to be at for the next flight. Southwest probably can only fly specific routes at specific time due to air traffic congestion and regulatory approvals, so can't always fly on a straight line to correct location. By the time they get to the correct place, planes may need maintenance and crews may need sleep. Solving this in close to optimum time is probably an NP-hard problem and company's existing software and employee training is not up to handling this edge case. So there are probably a lot of people pencilling in their best guess for who should go where and calling crews on the phone to let them know. Might take a while to get back to normal.