A wing or stabilizer of an aircraft , comprising: a box portion , comprising at least one spar and an outer skin coupled to the at least one spar; and at least one panel , comprising: an outer face-sheet , wherein in a fore-aft direction the outer face-sheet terminates at an outer free edge ; an inner face-sheet having no portion in contact with said outer face-sheet at the leading end of the at least one panel , wherein in the fore-aft direction the inner face-sheet terminates at an inner free edge , said inner free edge being spaced apart from said outer free edge at the leading end of the at least one panel ; and a core sandwiched between the outer face-sheet and the inner face-sheet ; wherein: the inner face-sheet comprises a cantilevered portion ; the cantilevered portion defines the inner free edge ; the cantilevered portion is fastened to the outer skin of the box portion ; and the inner face-sheet further comprises: a base portion ; and a transition portion , between the base portion and the cantilevered portion ; wherein a thickness of the base portion is less than a thickness of the cantilevered portion ; and a thickness of the transition portion increases from the thickness of the base portion to the thickness of the cantilevered portion . a box portion , comprising at least one spar and an outer skin coupled to the at least one spar; and at least one panel , comprising: an outer face-sheet , wherein in a fore-aft direction the outer face-sheet terminates at an outer free edge ; an inner face-sheet having no portion in contact with said outer face-sheet at the leading end of the at least one panel , wherein in the fore-aft direction the inner face-sheet terminates at an inner free edge , said inner free edge being spaced apart from said outer free edge at the leading end of the at least one panel ; and a core sandwiched between the outer face-sheet and the inner face-sheet ; an outer face-sheet , wherein in a fore-aft direction the outer face-sheet terminates at an outer free edge ; an inner face-sheet having no portion in contact with said outer face-sheet at the leading end of the at least one panel , wherein in the fore-aft direction the inner face-sheet terminates at an inner free edge , said inner free edge being spaced apart from said outer free edge at the leading end of the at least one panel ; and a core sandwiched between the outer face-sheet and the inner face-sheet ; wherein: the inner face-sheet comprises a cantilevered portion ; the cantilevered portion defines the inner free edge ; the cantilevered portion is fastened to the outer skin of the box portion ; and the inner face-sheet further comprises: a base portion ; and a transition portion , between the base portion and the cantilevered portion ; wherein a thickness of the base portion is less than a thickness of the cantilevered portion ; and a thickness of the transition portion increases from the thickness of the base portion to the thickness of the cantilevered portion . the inner face-sheet comprises a cantilevered portion ; the cantilevered portion defines the inner free edge ; the cantilevered portion is fastened to the outer skin of the box portion ; and the inner face-sheet further comprises: a base portion ; and a transition portion , between the base portion and the cantilevered portion ; wherein a thickness of the base portion is less than a thickness of the cantilevered portion ; and a thickness of the transition portion increases from the thickness of the base portion to the thickness of the cantilevered portion . a base portion ; and a transition portion , between the base portion and the cantilevered portion ; wherein a thickness of the base portion is less than a thickness of the cantilevered portion ; and a thickness of the transition portion increases from the thickness of the base portion to the thickness of the cantilevered portion . <EOS>