Aircraft, comprising: • a main body of a fuselage, • at least one sliding side door capable of moving in translation in a longitudinal direction D, said sliding side door being movable between a closed position in which said door is arranged towards a front part of the main body of said fuselage and an open position in which said door is arranged towards a rear part of the main body of said fuselage, • at least one fin (1, 11, 21, 31) emerging transversely from said main body of said fuselage substantially perpendicularly with respect to a vertical anteroposterior plane of symmetry P of said main body of said fuselage when said aircraft is positioned on a horizontal base, said at least one fin (1, 11, 21, 31) comprising a cutout (4, 14, 24, 34) that locally reduces a cross section of said at least one fin (1, 11, 21, 31) in a junction region of said at least one fin (1, 11, 21, 31), said junction region being arranged in the immediate vicinity of said main body of said fuselage of the aircraft, from which main body said at least one fin (1, 11, 21, 31) emerges transversely, said cutout (4, 14, 24, 34) being open at least in the region of an outer front face and an outer top face of said at least one fin (1, 11, 21, 31) and enabling a bottom portion of said sliding side door arranged in the open position to be received, characterized in that said cutout (4, 14, 24, 34) of said at least one fin (1, 11, 21, 31) comprises: • an inner bottom face (15, 25, 35) oriented substantially horizontally when said aircraft is positioned on a horizontal base and opening in the region of said outer front face of said at least one fin (1, 11, 21, 31), • an inner face (16, 26, 36) inclined towards the rear of said fuselage of the aircraft and extending between said inner bottom face (15, 25, 35) and said outer top face of said at least one fin (1, 11, 21, 31), and • an inner wall arranged substantially in parallel with and opposite said main body and engaging with said inner bottom face (15, 25, 35) and said inclined inner face (16, 26, 36), as well as with said outer front face and said outer top face of said at least one fin (1, 11, 21, 31). • a main body of a fuselage, • at least one sliding side door capable of moving in translation in a longitudinal direction D, said sliding side door being movable between a closed position in which said door is arranged towards a front part of the main body of said fuselage and an open position in which said door is arranged towards a rear part of the main body of said fuselage, • at least one fin (1, 11, 21, 31) emerging transversely from said main body of said fuselage substantially perpendicularly with respect to a vertical anteroposterior plane of symmetry P of said main body of said fuselage when said aircraft is positioned on a horizontal base, said at least one fin (1, 11, 21, 31) comprising a cutout (4, 14, 24, 34) that locally reduces a cross section of said at least one fin (1, 11, 21, 31) in a junction region of said at least one fin (1, 11, 21, 31), said junction region being arranged in the immediate vicinity of said main body of said fuselage of the aircraft, from which main body said at least one fin (1, 11, 21, 31) emerges transversely, said cutout (4, 14, 24, 34) being open at least in the region of an outer front face and an outer top face of said at least one fin (1, 11, 21, 31) and enabling a bottom portion of said sliding side door arranged in the open position to be received, • an inner bottom face (15, 25, 35) oriented substantially horizontally when said aircraft is positioned on a horizontal base and opening in the region of said outer front face of said at least one fin (1, 11, 21, 31), • an inner face (16, 26, 36) inclined towards the rear of said fuselage of the aircraft and extending between said inner bottom face (15, 25, 35) and said outer top face of said at least one fin (1, 11, 21, 31), and • an inner wall arranged substantially in parallel with and opposite said main body and engaging with said inner bottom face (15, 25, 35) and said inclined inner face (16, 26, 36), as well as with said outer front face and said outer top face of said at least one fin (1, 11, 21, 31).