[joeseeder]

Airbus systems have alternate law mode which kicks in when computers, sensors fail, read about Air France crash

[smadurange]

I think this is true. Also, in the Air Asia crash when pilot disengaged autopilot by mistake using a reset switch changing flight mode to manual.

As far as I know, if the autopilot can't make reliable decisions, it rings alarm bells and disengages fly-by-wire. Looks to me like quite elegant design.