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 a fan case having an annular casing element for encircling an array of fan blades and a hook projecting in a generally radially inward direction from the annular casing element. An annular fan track liner is provided comprising a first fan track liner panel positioned circumferentially adjacent a second fan track liner panel. A coupling connects the first fan track liner panel to the second fan track liner panel and the first fan track liner panel and the second fan track liner panel each comprise a groove along an axial face thereof and a portion of the coupling is received in each of said grooves.