Could Jack's dad coffin be empty cos. .. he's REALLY alive and/or the mysterious island demon's made him part of the ghoulscape. .. .OR

Could the airline have simply decided to send on the empty coffin to get this angry passenger off their backs so he'd make it on time for the funeral. .and they'd quietly held the REAL body behind until ALL the paperwork was clear?

I think it's because the father is now out -- he's a ghost now on the island -- because the island is where basically they're all dead and reborn. What a great episode that was. I have so many questions in my head -- great writing.