Just an example and sort of a rant about Southwest operations from a poster who usually is very supportive...

My wife was schedule to leave Houston yesterday at 5:05 pm, but by at least 3:45 pm, WN delays the flight because the arriving aircraft out of Midland has mechanical problems and the MAF -> HOU flight is cancelled. So, the HOU -> AUS flight is delayed to 7:30 while they wait on an aircraft that is coming out of maintenance. The aircraft finally rolls up to the gate just before 8:00 pm but the mechanical problem that was supposed to have been fixed actually wasn't. So, the lucky passengers get to wait another hour for an arriving aircraft to be repurposed to complete the flight.

Yeah, stuff happens. The problem is that she tried to get rerouted through DAL but all the flights to and from DAL were full. And apparently with such tight aircraft inventory, even one aircraft going out of service can cause major delays. Just more bad news when it comes to the unfortunate reality for passengers when it comes to no competition, full flights, and cramped seating.