A wing of an aircraft has a mainplane, which has an upper face, a lower face and an aerodynamically shaped area. The wing has an additional airfoil which is articulated on the mainplane and can be extended from a retracted state with a slot area being opened between the mainplane and the additional airfoil. The wing also has a variable-position slot-varying apparatus which is arranged on the lower face, forms a part of the aerodynamic profile of the additional airfoil or mainplane when the additional airfoil is extended, and at least partially covers the slot area between the mainplane and the additional airfoil on the lower face when the additional airfoil is in the retracted state. The slot-varying apparatus can be varied between a curved configuration, in which it forms a part of an aerodynamic profile, and an extended configuration, in which it at least partially covers the slot area.