Once upon a time ... not too long ago, certainly in my youth .... lifts had human beings employed to open and close metal gates and to press buttons to set in place the machinery necessary for the lift to move between floors.
This is now a bygone era, and may well make younger members of this forum snigger at the very idea.
So maybe, just maybe, the idea of a plane flight with no human on the flight deck is not so far-fetched after all ...