Fan containment system fitting around an array of radially extending fan blades mounted on a hub in an axial gas turbine engine. The fan containment system includes a fan case having an annular casing element for encircling the array of fan blades and a hook projecting in a radially inward direction from the annular casing element and positioned axially forward of the array of fan blades when the fan containment system fitted around fan blades. An annular fan track liner positioned substantially coaxial to the annular casing element. Clamping arrangement connects fan track liner to the hook. Clamping arrangement is configured under the condition that a fan blade impacts the fan track liner, the clamping arrangement releases connection between the hook and a portion of fan track liner so that a portion of the fan track liner can move towards the annular casing element to encourage the fan blade to impact the hook.