problem is for the skipper unless you have someone on board that can certify them as dead they are still alive even if stiff as a plank, so you have to act as if they are alive and get them to medical attention as quickly as possible.
Which might not be in the interests of some family's to be honest who might want them at destination so they don't have to get the body home.
There is a story out there of a crew loading an old bloke who was with his son. Son Chucked him in his seat and said he was fine just sleeping. The across water regional flight went ahead.
On landing crew got off and as you do caught up with pax in the arrivals hall just as son and dad were coming out to meet sister. Who turned out to be a doctor.
"When did he go?" she said while taking a neck pulse.
"In the taxi on the way to the airport" was the reply.