Abstract: The invention related to bearing structures of aircraft, in particular to an airtight fuselage. The inventive aircraft fuselage whose width is substantially greater than the height in the closed cross-section thereof comprises frames which are successively disposed along the fuselage and to which the external skin is fixed, stringers connected to the skin and frames and the external elements of the frames. Said fuselage is provided, along the length of the airtight part thereof, with longitudinal bearing arched structures which reinforce the top and lower parts of the fuselage, are disposed on the lateral sides and comprise connected to each other a lower longitudinal bearing element, vertical posts arranged on the frames at a given number of spacings and the top bearing elements provided with arched elements placed between the adjacent posts.