In aeronautics, bracing comprises additional structural members which stiffen the functional airframe to give it rigidity and strength under load. Bracing may be applied both internally and externally, and may take the form of struts, which act in compression or tension as the need arises, and/or wires, which act only in tension.
In general, bracing allows a stronger, lighter structure than one which is unbraced, but external bracing in particular adds drag which slows down the aircraft and raises considerably more design issues than internal bracing. Another disadvantage of bracing wires is that they require routine checking and adjustment, or rigging, even when located internally.
During the early years of aviation, bracing was a universal feature of all forms of aeroplanes, including the monoplanes and biplanes, which were then equally common. Today, bracing in the form of lift struts is still used for some light commercial designs where a high wing and light weight are more important than ultimate performance.