In accordance with the present invention, there is provided a passenger accommodation arrangement for aircraft which provides both a highly efficient use of available aircraft space and a high level of comfort for passengers. In particular, the novel arrangement allows passengers to easily and comfortably switch between sitting and sleeping positions. The arrangement provides for multiple compartments arranged transversely with respect to the longitudinal dimension of the aircraft. Each compartment includes a stair and multiple, individual passenger accommodation units arranged one above another on each side of the stair. Each unit contains structure which allows a passenger to switch between a sitting position, in which the passenger is supported on a seat surface, and a fully reposed position in which the passenger is supported on a substantially flat, horizontal sleeping surface. Conversion between sitting and sleeping positions is enabled by moveable sections which form part of the passenger bed in a first position and part of the passenger seat in a second position. Passenger units which are vertically adjacent to one another may include complementary and vertically aligned formations to optimize the usable height of the units.