Analysis and testing have been used to develop a flapping wing which can efficiently produce lift and thrust for ornithopter flight. With the assumption that the only imposed motion is dihedral flapping at its root, the wing's spanwise distribution of pitching and bending is due to its aeroelastic response. Numerical studies revealed criteria for efficient designs, which then guided the development and construction of an example wing tested in a windtunnel. The experimental results for average thrust and lift compared very favourably with the theoretical predictions, confirming that such aeroelastically tailored designs provide a means for achieving mechanical flapping-wing flight.