Also, "penetrate and patch" is definitely at work in the airline industry. Yes, airliners are well designed as safe systems, but every now and again a problem does occur, to varying degrees of seriousness, and when such a problem is identified, it is patched.

Defence in depth. Sure, design a system well. But "penetrate and patch" is another layer of protection. I mean, if you find your system is penetrated, what else can you do right now but patch it?