Abstract: Sleeping units such as bunks or cabins are arranged in a space efficient manner in the lower lobe of an aircraft, accessible from the main passenger cabin by a stairway or elevator. The space efficient arrangement of sleeping units can include bunks extending longitudinally along one side of a longitudinal aisle and bunks extending transversely of the aircraft at the other side of the aisle. Access to the transversely extending bunks can be by short cross-aisles. At least one portion of the passenger compartment can have a floor lowered relative to the normal cargo floor to provide additional headroom in the aisle, while another portion of the sleeping compartment can rest on the cargo floor for conversion between a passenger rest area configuration and a standard cargo carrying configuration.