An internal arrangement of aircraft fuselage walls supports two longitudinal auxiliary passage ducts at the upper part of the fuselage and on each side of its longitudinal plane of symmetry. The arrangement includes a longitudinal central element forming a dome connecting the structural ducts, an interior ceiling panel situated under the dome and facing toward the cabin, and two lateral cover panels. A lower edge of each lateral panel is articulated with respect to the fuselage so that it may occupy a raised position in which it is connected to a respective one of the structural ducts near an upper edge of the structural duct and a lowered position in which it is distant from the structural duct. Also, the upper edge of each lateral panel is extended, in the raised position, beyond the structural duct to cover the corresponding longitudinal edges of the dome and the ceiling panel.