Re: Southwest's position (last November)
"Why would an airline spend money on a optional extra unless they thought it was safety critical option?"
Well, that's on Boeing. One of the selling points of derivative models is that they will be similar enough to the older versions that training and procedures manuals won't have to be changed (much). It sounds like Boeing thought they could add this stability augmentation system and have it just putter along in the background without having to bother the flight crews with the details.
SWA, for whatever reason, seems to have sprung for the additional indication (really just a software generated dial on an existing display) and some class time on what it means. Their motivation may have had nothing to do with MCAS faults, but having that additional information might have proven to be invaluable. Something about hindsight being 20-20.