Denti.... my impression was it was for the whole flight, even so I not sure I would be happy for a single pilot in the cruise. In the case of the Air France A330 accident, two pilots couldn't cope and even when the captain was called onto the flight deck, having been resting in a bunk, he couldn't wotk out what was happening. I think the study looks into if in the event of incapcitation, a ground based pilot would fly the aircraft. I think for short haul there is never any justification to leave the flight deck for a variety of reasons.