Method for manufacturing an integrated composite trailing edge of an aircraft, the trailing edge comprising: an integrated main structure comprising: ∘ an upper cover, ∘ lower flanges, and ∘ a set of ribs extending between the upper cover and the lower flanges, - a set of sandwich type lower panels attachable to the lower flanges of the integrated main structure, the method comprising the following steps: a) providing a set of prepreg laminated preforms of composite material over a set of tool modules, said tool modules having a hollow located at their upper part for receiving a sandwich core, the tool modules being configured so that each prepreg laminated preform configures a double C-shaped laminated preform having an upper section with a recess corresponding with the hollow, two primary flanges and two secondary flanges, the upper section configured for partly forming a segment of the upper cover of the integrated main structure, the two primary flanges configured for partly forming the ribs and the two secondary flanges configured for forming the lower flanges of the integrated main structure, the double C-shaped laminated preform being formed by providing a flat prepreg laminate over the tool module followed by a forming process of said flat laminate over the tool module for forming the double C shape and the recess and during the forming process a membrane is located over the tool module being pressed against the tool module by means of the vacuum provided by a general air port while a male tool presses the flat prepreg laminate against the hollow of the tool module for forming the recess of the C-shaped laminated preform, b) providing a set of sandwich cores into the recesses of the double C-shaped laminated preforms, c) aligning the set of tool modules so that adjacent primary flanges are located together, d) providing rovings to fill up the space in the radii between adjacent primary flanges, e) providing a prepreg laminate on top of the aligned set of tool modules, f) providing lower prepreg laminates against two consecutive secondary flanges, and g) applying a curing process to cocure said laminated preforms so that the integrated main structure of the trailing edge is formed. an integrated main structure comprising: ∘ an upper cover, ∘ lower flanges, and ∘ a set of ribs extending between the upper cover and the lower flanges, ∘ an upper cover, ∘ lower flanges, and ∘ a set of ribs extending between the upper cover and the lower flanges, - a set of sandwich type lower panels attachable to the lower flanges of the integrated main structure, a) providing a set of prepreg laminated preforms of composite material over a set of tool modules, said tool modules having a hollow located at their upper part for receiving a sandwich core, the tool modules being configured so that each prepreg laminated preform configures a double C-shaped laminated preform having an upper section with a recess corresponding with the hollow, two primary flanges and two secondary flanges, the upper section configured for partly forming a segment of the upper cover of the integrated main structure, the two primary flanges configured for partly forming the ribs and the two secondary flanges configured for forming the lower flanges of the integrated main structure, the double C-shaped laminated preform being formed by providing a flat prepreg laminate over the tool module followed by a forming process of said flat laminate over the tool module for forming the double C shape and the recess and during the forming process a membrane is located over the tool module being pressed against the tool module by means of the vacuum provided by a general air port while a male tool presses the flat prepreg laminate against the hollow of the tool module for forming the recess of the C-shaped laminated preform, b) providing a set of sandwich cores into the recesses of the double C-shaped laminated preforms, c) aligning the set of tool modules so that adjacent primary flanges are located together, d) providing rovings to fill up the space in the radii between adjacent primary flanges, e) providing a prepreg laminate on top of the aligned set of tool modules, f) providing lower prepreg laminates against two consecutive secondary flanges, and g) applying a curing process to cocure said laminated preforms so that the integrated main structure of the trailing edge is formed.