An efficient flying device having flapping wings, an ornithopter, which uses many of the principles seen in bird flight, is presented herein. The wings are highly flexible, translationally stable and oscillate as a natural pendulum. Described as a springboard, the wings have a singular natural frequency, and a pumping means drives the wings at that frequency. Feedback means are described by which to accomplish this, whereby deflection of the wing affects an escapement mechanism which controls the timing and direction of the pumping means. Wing design is described whereby camber, flexure, torsion and directionality of wing components affect efficient propulsion, lift and differential reactivity with air during downstrokes and upstrokes. A crook element in the wing spar at a location proximal to the body of the device redirects vertical oscillation to horizontal. Other features are addressed, such as rearward vortex production and reaction, a double aerofoil wing construction, lateral and vertical wing curvature, rearward wing and featherlike element flexure to produce thrust, and connection of separate elastic elements to reduce power requirements.