When airlines change the back of the plane, it's usually to pack in more passengers or install something you can give them money to enjoy. For those who turn left as they board, life aloft is swankier than ever.

But last week at the Aircraft Interiors Expo in Hamburg, economy fliers got a bit of good, if not quite glamorous, news. One of the world's largest plane builders, Airbus, and cabin builder Zodiac Aerospace are going to start building beds for hire. Full-size, lay-out-flat beds—no business or first-class ticket required.

In an environment as cramped as a plane cabin, Zodiac's designers had to go downstairs, into the cargo hold, to find extra space.