[nemomarx]

Can you fit more people in horizontal than if they stood up and you had little straps to hang onto like a subway?

[nostrademons]

In theory yes because you can use the space at the top that would otherwise be above people's heads. No guarantee they get to their destination alive though.

[rtkwe]

Once you include space to get people to the restroom though and to allow them to breath during the flight I think you get a higher density while standing vs laying down.

[butlike]

You can just lay them ass-to-mouth and then stack them. Come on, the slave ships and Dutch East India company taught us that one.