This is a hard one...
My company's procedures are that in the absence of a qualified doctor, noone else can confirm death and halt resucitation attempts, if this means we do CPR for 3 hours over the atlantic then so be it. In this case we would not seek to hide the body anywhere as until the last minute we would be working to preserve life. Im not sure what would happen if a doctor was onboard and did confirm the passenger was dead. Our flights are often full and I'm not sure how other passengers would react if a dead passenger had to be left in the next seat to them until we could land (we have no crewrest areas). Hope I never have to be in this situation but in this job we never know what might have to deal with..