An airfoil having two (2) basic components, a sail and spoiler, associated with the leading edge of the sail, is herein disclosed. This unique airfoil design has application in flexible wing aircraft (i.e., ultralites), sport parachutes and sport kites. In the typical sport kite embodiment of this invention, there will generally be at least three (3) aerodynamic flight control surfaces: a sail, a keel, and a flexible resilient spoiler attached to the leading edge of the sail. The sail material is itself resilient, however, sufficiently rigid to maintain a preset configuration without the need for struts, spars or extrinsic physical support. A spoiler, which is located along the entire leading edge of the sail, provides additional structural reinforcement to the sail while undergoing controlled deformation in gusty or high winds. The effect of such deformation of the spoiler causes the sail to stall before any physical damage can occur. The resiliency of the spoiler immediately, thereafter, returns the sail to pre-stall configuration, and flight is thereupon resumed without physical damage to the kite. Under certain conditions, it may be desirable to further enhance the inherent physical strength of the sail along the centerline of the sail coincident with the area of the stress imparted upon the sail by the keel. This is readily accomplished by affixing an additional section of sail construction material, or its equivalent, along the topside surface of the sail, opposite to and coincident with the placement of the keel.