A fan containment system having a generally cylindrical fan case including a hook projecting in a generally radially inward direction and positioned axially forward of a radial array of fan blades; a fan track liner disposed on the radially inner surface of the fan case; and a panel which is positioned axially rearward of the hook and positioned axially forward of the radial array of fan blades and forms a substantially continuous air washed surface with the fan track liner. The panel is temporarily deformable so as to absorb the impacts of any foreign bodies, which enter the gas turbine engine, without compromising the structural integrity of the panel while being weak enough so that in the event that one of the fan blades is released from the hub, the fan blade tip of the detached fan blade is not inhibited from moving radially outward of the hub.