The invention relates to a seat that can be converted into a sleeping-berth. The invention comprises a block (2) of adjacent seats (3) that can be converted individually from an armchair configuration to a horizontal sleeping configuration, in which the seats (3) are arranged and oriented substantially in the same direction. The longitudinal axes (34) of two seats (3) in the sleeping configuration converge towards a point located at a distance in front of the seats, such that, in the sleeping configuration, the feet areas in front of the seats, where the seat occupant's feet are positioned during normal use, are stacked.; The sleeping planes (35) of the seats of one block are offset vertically and extend into rest surfaces (42) for the feet areas (41) which are provided in a column (4) disposed between the seat backs of the block in front, thereby allowing the distance between seats to be reduced while retaining full comfort, and providing an improved passenger cabin layout.