Because of the pressure difference at the ends of all finite-span wings, wing tip vortices are generated in flight, leading to downwash and so-called induced drag. To reduce the impact of this phenomenon, many types of wing planforms and tip shapes have been flown over the years. It is now common practice in civil airliners to have complex wing tip devices to help the aerodynamic performance of the aircraft, albeit with some consequences for structural loading. Since, generally, we use full span spars and need to terminate them in some structurally efficient way, we routinely place a wing rib at the outermost edge of each wing. It is then a simple matter using SLS or fused deposition modeling (FDM) printing to create quite complex additional tip devices to improve the aerodynamics of the wing. We generally use computational fluid dynamics (CFD) models and wind tunnel testing to refine these shapes for best performance, see, again, Figure 3.2 and also Figure 3.12. It is often possible to reduce the overall induced drag of a wing by 20% with careful tip and planform taper design.