Disc wheels are designed to minimize aerodynamic drag. Pitching moment coefficient is fundamental to the definition of aerodynamic center of an airfoil. Drag can also be reduced by covering the bicycle with an aerodynamic fairing. A pitot inlet is little more than a tube with an aerodynamic fairing around it. Further refinements to the aerodynamic profile yielded little improvement. The fairing has been widened by as part of the aerodynamic styling. This helped to reduce drag and improve aerodynamic efficiency. New engine technology and aerodynamic modifications allow longer range. Benefits claimed include greater comfort and aerodynamic efficiency. Reducing aerodynamic drag was another primary design goal. Such an aircraft is capable of maneuvers that are impossible with a purely aerodynamic design. They were designed with the aid of low-speed aerodynamic engineering design principles. Dynamic aeroelasticity studies the interactions among aerodynamic, elastic, and inertial forces. This resistance is important in maintaining the aerodynamic shape of the sail. Both vehicles now featured softer lines as part of a more aerodynamic design.