Double decker seat layout in economy section is still being worked on. To borrow a phrase from The 70's Show: "Butt face gas attack" comes to mind.
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A Man Wants To Solve The Problem Of Tiny Airplane Seats By Stacking Passengers On Top Of Each Other - The Autopian
Flying economy sucks, a startup might have the answer. Chaise Longue wants to stack passengers on top of each other and Airbus wants to help