A fan casing for a turbofan engine including an annular casing component of composite material including a body portion having an outwardly directed stiffening flange at one end, the stiffening flange being connected to the body portion by a radially outwardly stepped region, the fan casing also including a metallic ring which is coaxial with the annular casing component, the metallic ring being situated at least partially within the stepped region and being secured to the annular casing component.