 The highest aspect ratio man-made wings are aircraft propellers, in their most extreme form as helicopter rotors.To measure the wingspan of a bird, a live or freshly-dead specimen is placed flat on its back, the wings are grasped at the wrist joints, ankles and the distance is measured between the tips of the longest primary feathers on each wing.The wingspan of an insect refers to the wingspan of pinned specimens, and may refer to the distance between the centre of the thorax to the apex of the wing doubled or to the width between the apices with the wings set with the trailing wing edge perpendicular to the body.