A casing structure interposed between the engine and the nacelle of an aircraft, the casing structure including a shroud surrounding the engine and including a plurality of sectors; at least one radial arm providing the connection to the nacelle; and a plurality of fasteners for securing the plurality of shroud sectors to one another or to the at least one radial arm; the plurality of fasteners including a plurality of connection tabs, each provided with two parallel series of holes for receiving two respective series of headed bolts, a first series passing through a corresponding set of orifices of one shroud sector, and a second series passing through a corresponding set of orifices of an adjacent shroud sector or an adjacent radial arm.