A central wing box for an aircraft, including a top panel, a bottom panel, a front spar, a rear spar, and at least one secondary rib. A secondary rib includes two stiffeners, a first stiffener extending adjacent to the top panel and to one of the front spar and the rear spar, and a second stiffener extending adjacent to the bottom panel and to the other of the front spar and the rear spar. A reduced number of components can be employed, thereby simplifying the construction of the central wing box of an aircraft, particularly the installation of the secondary ribs.