A gas turbine engine comprising: a fan section having a fan; and a containment zone encircling the fan, the containment zone comprising: a containment zone casing; a ballistic liner adhered to a containment zone casing located radially outward of the ballistic liner, the ballistic liner being composed of a plurality of ring segments (220a-e) located radially outward of the fan; wherein each of the plurality of ring segments include; two opposing circumferential ends (230a, 230b) including a first circumferential end and a second circumferential end opposite the first circumferential end; a radially inward surface extending from the first circumferential end to the second circumferential end, a radially outward surface opposite the radially inward surface, the radially inward surface extending from the first circumferential end to the second circumferential end; and a joint at each of the circumferential ends, the joint extending from the radially inward surface to the radially outward surface, and wherein the plurality of ring segments are arranged circumferentially around the fan section and the circumferential ends of each of the plurality of ring segments meet at joints to form the ballistic liner, characterised in that the plurality of ring segments are oriented radially in layers, and wherein each joint is a butt joint and the butt joints are staggered such that the butt joints of each of the plurality of ring segments are not aligned radially outward through the layers. a fan section having a fan; and a containment zone encircling the fan, the containment zone comprising: a containment zone casing; a ballistic liner adhered to a containment zone casing located radially outward of the ballistic liner, the ballistic liner being composed of a plurality of ring segments (220a-e) located radially outward of the fan; wherein each of the plurality of ring segments include; two opposing circumferential ends (230a, 230b) including a first circumferential end and a second circumferential end opposite the first circumferential end; a radially inward surface extending from the first circumferential end to the second circumferential end, a radially outward surface opposite the radially inward surface, the radially inward surface extending from the first circumferential end to the second circumferential end; and a joint at each of the circumferential ends, the joint extending from the radially inward surface to the radially outward surface, and wherein the plurality of ring segments are arranged circumferentially around the fan section and the circumferential ends of each of the plurality of ring segments meet at joints to form the ballistic liner, characterised in that the plurality of ring segments are oriented radially in layers, and wherein each joint is a butt joint and the butt joints are staggered such that the butt joints of each of the plurality of ring segments are not aligned radially outward through the layers. a containment zone casing; a ballistic liner adhered to a containment zone casing located radially outward of the ballistic liner, the ballistic liner being composed of a plurality of ring segments (220a-e) located radially outward of the fan; wherein each of the plurality of ring segments include; two opposing circumferential ends (230a, 230b) including a first circumferential end and a second circumferential end opposite the first circumferential end; a radially inward surface extending from the first circumferential end to the second circumferential end, a radially outward surface opposite the radially inward surface, the radially inward surface extending from the first circumferential end to the second circumferential end; and a joint at each of the circumferential ends, the joint extending from the radially inward surface to the radially outward surface, and wherein the plurality of ring segments are arranged circumferentially around the fan section and the circumferential ends of each of the plurality of ring segments meet at joints to form the ballistic liner, characterised in that the plurality of ring segments are oriented radially in layers, and wherein each joint is a butt joint and the butt joints are staggered such that the butt joints of each of the plurality of ring segments are not aligned radially outward through the layers. two opposing circumferential ends (230a, 230b) including a first circumferential end and a second circumferential end opposite the first circumferential end; a radially inward surface extending from the first circumferential end to the second circumferential end, a radially outward surface opposite the radially inward surface, the radially inward surface extending from the first circumferential end to the second circumferential end; and a joint at each of the circumferential ends, the joint extending from the radially inward surface to the radially outward surface, and wherein the plurality of ring segments are arranged circumferentially around the fan section and the circumferential ends of each of the plurality of ring segments meet at joints to form the ballistic liner, characterised in that the plurality of ring segments are oriented radially in layers, and wherein each joint is a butt joint and the butt joints are staggered such that the butt joints of each of the plurality of ring segments are not aligned radially outward through the layers.