At the risk of “trying to control a debate by controlling the meaning of the terms,” (not a thing I would want to do) let me comment on my use of the term “quality assurance”.

Quality assurance refers to those actions taken to provide confidence that (in this case) the commercial airline flight will “satisfy customer requirements.” The key word in the definition is “confidence.”

Neither I nor the FAA would currently be “confident” in the safety of a completely automated commercial aircraft. Nor would a single pilot be enough. However, with two pilots we do have the required subjective(!) confidence. Why? Fundamentally, for exactly the reason that Rob Bach stated: “People make mistakes.” All the other work-load/fatigue/size issues, while of practical importance, are secondary to this fundamental truth.

Risk is probability multiplied by consequence. The consequences of commercial airline pilot mistakes are pretty high. The copilot is there to reduce the probability of a mistake to a level that gives us the required confidence against the risk. Automate or apply technology to all the work-load/fatigue/size/etc issues you care to and you still get two pilots in the plane in order to provide the required confidence against mistakes.

And checklists are the same thing. Confidence against errors. That is, we are confident they help prevent overlooking something — is the fuel switch set to an empty tank?

So yes, while not disagreeing with anything Rob said, I do think it’s basically a quality assurance issue.