A fan containment system for fitment around an array of radially extending fan blades mounted on a hub in an axial gas turbine engine. The fan containment system comprises an annular casing element for encircling an array of fan blades. An annular fan track liner is positioned substantially coaxial to the annular casing element. A hook projects in a generally radially inward direction from the annular casing element and is positioned axially forward of an array of fan blades when the fan containment system is fitted around said fan blades. Tabs protrude from the hook in a generally rearward direction and are spaced circumferentially along the hook. Fasteners connect the fan track liner to the tabs. The fasteners are configured so as to permit movement of the fan track liner towards the annular casing element when the fan track liner is impacted by a released fan blade.