A wing for an aircraft having a fuselage, the wing comprising: a main wing including a main wing tip; and a winglet system attached to the main wing tip, the winglet system including: an upper winglet having an upper winglet tip outboard of the main wing tip; and a lower winglet having a lower winglet tip outboard of the main wing tip, the upper winglet tip of the upper winglet being disposed higher than the lower winglet tip of the lower winglet relative to the main wing tip; wherein: the upper and lower winglets are staggered along a chord of the main wing tip; the upper and lower winglets overlap one another along the chord of the main wing tip; a spanwise profile of the lower winglet extending along the leading edge of the lower winglet has a midpoint, a slope of the spanwise profile at a point outboard of the midpoint being inclined more upwardly than a slope of the spanwise profile at the midpoint when extending away from the fuselage; the spanwise profile of the lower winglet extending along the leading edge of the lower winglet being tangent-continuous with the leading edge of the main wing when viewed along the chord of the main wing tip; and the upper and lower winglets both extend upwardly relative to the main wing tip. a main wing including a main wing tip; and a winglet system attached to the main wing tip, the winglet system including: an upper winglet having an upper winglet tip outboard of the main wing tip; and a lower winglet having a lower winglet tip outboard of the main wing tip, the upper winglet tip of the upper winglet being disposed higher than the lower winglet tip of the lower winglet relative to the main wing tip; wherein: the upper and lower winglets are staggered along a chord of the main wing tip; the upper and lower winglets overlap one another along the chord of the main wing tip; a spanwise profile of the lower winglet extending along the leading edge of the lower winglet has a midpoint, a slope of the spanwise profile at a point outboard of the midpoint being inclined more upwardly than a slope of the spanwise profile at the midpoint when extending away from the fuselage; the spanwise profile of the lower winglet extending along the leading edge of the lower winglet being tangent-continuous with the leading edge of the main wing when viewed along the chord of the main wing tip; and the upper and lower winglets both extend upwardly relative to the main wing tip. an upper winglet having an upper winglet tip outboard of the main wing tip; and a lower winglet having a lower winglet tip outboard of the main wing tip, the upper winglet tip of the upper winglet being disposed higher than the lower winglet tip of the lower winglet relative to the main wing tip; wherein: the upper and lower winglets are staggered along a chord of the main wing tip; the upper and lower winglets overlap one another along the chord of the main wing tip; a spanwise profile of the lower winglet extending along the leading edge of the lower winglet has a midpoint, a slope of the spanwise profile at a point outboard of the midpoint being inclined more upwardly than a slope of the spanwise profile at the midpoint when extending away from the fuselage; the spanwise profile of the lower winglet extending along the leading edge of the lower winglet being tangent-continuous with the leading edge of the main wing when viewed along the chord of the main wing tip; and the upper and lower winglets both extend upwardly relative to the main wing tip. the upper and lower winglets are staggered along a chord of the main wing tip; the upper and lower winglets overlap one another along the chord of the main wing tip; a spanwise profile of the lower winglet extending along the leading edge of the lower winglet has a midpoint, a slope of the spanwise profile at a point outboard of the midpoint being inclined more upwardly than a slope of the spanwise profile at the midpoint when extending away from the fuselage; the spanwise profile of the lower winglet extending along the leading edge of the lower winglet being tangent-continuous with the leading edge of the main wing when viewed along the chord of the main wing tip; and the upper and lower winglets both extend upwardly relative to the main wing tip.