There's also the fun wrinkle that not all crews or crew members are current on ratings (ie training courses) to operate all types/versions of planes the airline

There's also the fun wrinkle that not all crews or crew members are current on ratings (ie training courses) to operate all types/versions of planes the airline as in service. You also need sufficient open gates of the right type in the right place during the right time window or you idle a plane (which can then idle a crew). It's pretty easy to imagine how such a system which may work at a certain level of load can be tipped into a runaway scenario. As a systems person I'd be an interested reader if Southwest were to someday release an incident analysis and post-mortem of the type that good IT organizations do.