I've travelled on night trains in Europe a bunch of times in a 6 bed compartment, and the solution is pretty simple. When you book a ticket, you can choose your

I've travelled on night trains in Europe a bunch of times in a 6 bed compartment, and the solution is pretty simple. When you book a ticket, you can choose your preferred bed (top / middle / bottom), and there's a checkbox you can tick if you absolutely need the bottom bed. Somehow it all works out. It's really neat, because if you're travelling in a group and don't want to go to bed right away you can fold the top beds up and use the bottom beds as comfy benches. The problem with putting the same thing on an airplane is that it needs a lot of space. Seats offer way more density than bunk beds.