Originally Posted by
Cromely
Just a guess, but it may have something to do with vehicle shape.
A train has straight sides and is just as wide at the ceiling level as it is at the floor level. An airplane -- not so much.
While you may be able to get 5 across seating at floor level, you might not be able to do that 5 feet above floor level.
If you sleeping berths in an airplane like they sometimes to on trains, I would imagine that those in upper level compartmetns would have to be shorter than those in lower level compartments.
Cromely.
How is this matter handled on a Boeing 307? Pressurized, rounded fuselage. Of course, 307 is (slightly) wider than 707.
Of course, single level berths would not have that problem.