[seanmcdirmid]

Safety often comes via overwhelming redundancy and back up protections. The human should do X, but if they don't do X, another system will do Y to save the plane, and if that system fails, then another system will do Z...

Single points of failure should be avoided. Like in driving, things should work out if driver A or driver B does the right thing, or if the road is designed right, or if pedestrians are following reasonable rules, you just try to make all those things true, so if any of them are not, it isn't a disaster.

[MaxBarraclough]

This even has a catchy name: the Swiss cheese model.

https://en.wikipedia.org/wiki/Swiss_cheese_model