I don't think there is any technical reason why we couldn't one day have pilotless airliners - I feel it is more about cost and being human.
We are complex biomechanical computers that need a considerable amount of programming and environmental exposure to become competent at all respects of operating an air transport. The level of AI required to replicate this I would posit as being "strong". Once this level is reached, we're probably into the scenario of a "technological singularity" anyway, so not much point worrying! Anything a human could do could be done better by an AI...
Being a good pilot has long been about more than the physical aspects of aircraft control; indeed, automation of these functions has been around for a significant part of the history of aviation. The cognitive aspects of decision making have been studied for a much shorter period, however.