Abstract: A wing assembly in an aircraft includes a pair of wings and a winglet situated at each of the wing tips, the winglets or portions thereof being movably mounted. In order to avoid the need for providing structural reinforcement for the wings to accommodate the additional bending moments acting on the wings due to the presence of the winglets, a system is provided for automatically moving the winglets between a first position wherein each winglet has a first aerodynamically optimal angle of attack and a second position wherein each winglet has a second minimal angle of attack wherein the winglets add substantially no bending moment to the wings, the winglets being so automatically moved in response to the stress acting on the wing.