A nacelle (250; 350; 450; 550) configured to encircle an engine about an axis of rotation, comprising: an inlet cowling (202; 302; 402; 502) defining an inlet of the nacelle, wherein the inlet cowling (202; 302; 402; 502) comprises an inlet cowling external surface (204; 304; 404; 504), defining the outermost circumferential surface of the inlet cowling (202; 302; 402; 502), an inlet cowling maximum point (207; 307; 407; 507), which is the most radially outward point of the inlet cowling external surface, and an inlet cowling aft edge (210; 310; 410; 510), wherein the inlet cowling aft edge (210; 310; 410; 510) comprises an aft edge length (214; 314; 414), which is a length extending in a radial direction, and a radially outermost point (205; 305; 405; 505) of the inlet cowling aft edge (210; 310; 410; 510); and a boat tail cowling (230; 330; 430; 530) disposed aft of the inlet cowling (202; 302; 402; 502), wherein the boat tail cowling (230; 330; 430; 530) comprises a boat tail cowling external surface (232; 332; 432; 532), defining the radially outermost circumferential surface of the boat tail cowling (230; 330; 430; 530) and a boat tail cowling forward edge (224; 324; 424; 524), the boat tail cowling forward edge (224; 324; 424; 524) having a forward edge length (226, 426), which is a length extending in a radial direction, and a radially outermost point (227; 536) of the boat tail cowling forward edge (224; 324; 424; 524), wherein the boat tail cowling forward edge (224; 324; 424; 524) is disposed adjacent to the inlet cowling aft edge (210; 310; 410; 510), characterised in that the forward edge length is smaller than the aft edge length, forming a step (212; 312; 412), the step (212; 312; 412) consisting of a portion of the inlet cowling aft edge (210; 310; 410; 510) that is radially outward of the boat tail cowling forward edge (224; 324; 424; 524), said step being formed between the radially outermost point of the inlet cowling aft edge and the radially outermost point of the boat tail forward edge. an inlet cowling (202; 302; 402; 502) defining an inlet of the nacelle, wherein the inlet cowling (202; 302; 402; 502) comprises an inlet cowling external surface (204; 304; 404; 504), defining the outermost circumferential surface of the inlet cowling (202; 302; 402; 502), an inlet cowling maximum point (207; 307; 407; 507), which is the most radially outward point of the inlet cowling external surface, and an inlet cowling aft edge (210; 310; 410; 510), wherein the inlet cowling aft edge (210; 310; 410; 510) comprises an aft edge length (214; 314; 414), which is a length extending in a radial direction, and a radially outermost point (205; 305; 405; 505) of the inlet cowling aft edge (210; 310; 410; 510); and a boat tail cowling (230; 330; 430; 530) disposed aft of the inlet cowling (202; 302; 402; 502), wherein the boat tail cowling (230; 330; 430; 530) comprises a boat tail cowling external surface (232; 332; 432; 532), defining the radially outermost circumferential surface of the boat tail cowling (230; 330; 430; 530) and a boat tail cowling forward edge (224; 324; 424; 524), the boat tail cowling forward edge (224; 324; 424; 524) having a forward edge length (226, 426), which is a length extending in a radial direction, and a radially outermost point (227; 536) of the boat tail cowling forward edge (224; 324; 424; 524), wherein the boat tail cowling forward edge (224; 324; 424; 524) is disposed adjacent to the inlet cowling aft edge (210; 310; 410; 510), characterised in that the forward edge length is smaller than the aft edge length, forming a step (212; 312; 412), the step (212; 312; 412) consisting of a portion of the inlet cowling aft edge (210; 310; 410; 510) that is radially outward of the boat tail cowling forward edge (224; 324; 424; 524), said step being formed between the radially outermost point of the inlet cowling aft edge and the radially outermost point of the boat tail forward edge.