The door comprises a panel (14) formed from two rigid parts (14a, 14b) hinged to each other edge to edge. A first part (14a) of these two parts is connected to the aircraft structure through a pivot pin (20) and a control means (22) is inserted between this first part (14a) and the structure. A kinematic control mechanism (16) connects the two parts (14a, 14b) to the aircraft structure, so as to enable progressive and controlled folding of these parts when opening the door. Thus the landing gear door can be opened and closed without any risk of it coming into contact with the wheels when the landing gear is extended.