An optimized leading edge for an aircraft lifting or supporting surfaces, such as wings and stabilizers, wherein the leading edge includes inboard and outboard leading edge sections that are span-wise arranged so as to form together an aerodynamic surface of the leading edge. Each of the leading edge sections includes a skin panel and a support structure formed by spars that are internally arranged in the skin panel. These two support structures are designed taking into account the different load requirements of those two different sections, so that the number of spars in each leading edge section is progressively reduced from root to tip of the leading edge, in such a way that the support structure of the outboard leading edge section, has less spars than the inboard leading edge section. Hence the weight of the leading edge is reduced while still maintaining the required structural behavior.