From a November 29, 2018 story - Southwest airlines were activating a factory-installed option on delivered aircraft to "guard against any erroneous sensor data

From a November 29, 2018 story - Southwest airlines were activating a factory-installed option on delivered aircraft to "guard against any erroneous sensor data that may activate the jet's controversial stall protection system..." https://theaircurrent.com/aviation-safety/southwest-airlines-is-adding-new-angle-of-attack-indicators-to-its-737-max-fleet/ https://theaircurrent.com/aviation-safety/southwest-airlines... The article notes that the airline has opted for an upgraded avionics suite that low-cost airlines have, for the most part, forgone.