Arranging for a CC to guard the cockpit door when one pilot is unavoidably absent is such a mitigation, which has the added benefits of being immediately available at zero cost. Arguing that it is pointless because it may not guarantee a repeat is a kindergarten reaction.
Really, this is elementary logic.
If adding the CC was "zero risk", I might agree.
As the excellent article above states:
Of course, in a
PR attempt to be seen to be “doing something”, most airlines, worried about their profit margins and perceptions of the flying public, are now introducing a policy of always having two crew members on the flight deck (already common in the USA). This cheap and immediate measure seems a sensible policy at first sight, but clearly the law of unintended consequences applies here as well. What if the cabin crew member is the rogue member of staff, locks the door, restrains the remaining seated pilot and takes control of the aircraft to nose-dive it into the ground? Somebody with minimal screening on a zero hour contract? (the reality in low-cost airlines, where there is a high turn-over of cabin crew because of the poor working conditions).
It requires a "risk assessment" of the variables, and a conclusion.
If it was such "elementary logic" why did EASA/CAA require the airlines not only to review their risk assessment, but if they added the "2 in cockpit rule" the added risks of that must be assessed and mitigated?