[SamuraiScot]

there’s no other place to put the dead passenger except back in their seat.

I'm not convinced of that. How about the hold? Would need a sealed, pressurized container of some sort--but a back-up fridge would qualify for that, and you know any airplane has some of those.

Might not want to use that particular unit for food after that. . .

[wildcard_redneck]

I don’t think the hold is available for access from the passenger compartment

[PGR88]

I agree that airlines do not have contingencies for storing dead people.

According to the American Journal of American medicine, the mortality rate from in-flight medical emergencies is 0.21 deaths per million passengers (Jones & Lee, 2023).

there’s something like 800 million passenger flights domestic and international for US airlines

so that’s around 168 deaths in-flight (domestic and Intl) that US airlines have to deal with. FWIW, the number of in flight health emergencies is much higher - about 18 per million. Obviously, few of those result in immediate death.

So for 168 total deaths, are aircraft builders and airlines going to go to the probably huge cost of designing, building, training staff, etc... for on-board morgues/caskets/cold storage? Probably not