A high-lift device surface and associated method of designing the high-lift device surface is described. The flap can be attached to a wing on aircraft. The method can involve determining a manufactured shape of the flap. The manufactured flap shape can be deflected in some manner, such as bent or twisted, so that under selected flight conditions, such as cruise, the manufactured flap shape morphs into a second desired shape that satisfies specified constraints, such as geometric and sealing constraints. An advantage of the approach is that the flap doesn't have to be mechanically forced, using mechanical elements, into the second desired shape. The elimination of the mechanical elements results in weight and cost savings to aircraft on which the flap is deployed.