Just for background: the Air France flight referenced (AF447) did in fact have the kind of software fail-safes you're describing, the aircraft entered alternate

Just for background: the Air France flight referenced (AF447) did in fact have the kind of software fail-safes you're describing, the aircraft entered alternate law (ALT2) when the bad sensor input was detected and several automated flight systems were disabled (including envelope protection). The pilots were notified of this. There's actually a lot of reasons why AF447 crashed[0], so I won't attempt to [badly] summarize it here, but I will say it wasn't simply an equipment malfunction or computer problem. That's just what started the entire chain of events that ultimately lead to the crash. [0] https://en.wikipedia.org/wiki/Air_France_Flight_447#Final_report https://en.wikipedia.org/wiki/Air_France_Flight_447#Final_re...