Bird wings were doing it long before airplanes existed. Long before man existed, for that matter. The inner half of the wing gives the needed lift. It is curved on top, more or less flat on the underside. The air going over the top of the wing’s upward curve has to travel farther than the air going in a nearly straight line underneath. Hence, the air above must go faster, and thereby thins out. This means less pressure on top, more underneath. This greater pressure underneath pushes the wing up, giving lift. Sea birds, headed into a strong wind, wings motionless, steadily gain altitude because of the lifting power of this curvature of the inner half of their wings. The designers of airplane wings copied this curvature to give their machines lift—but God did it first, when he created birds.
One marvel of creation man has not succeeded in copying: that biological helicopter called a hummingbird. It flies forward, backward, sideways, upside down, or hovers motionless, all because of the way its wings work. It also uses wing curvature for lift, but with an amazing difference. The wings are rather stiff, except at the shoulder joint. They pivot so freely at the shoulder joint that they can turn 180 degrees. Thus one surface is up when the wing moves forward, the other surface up when it moves backward. Yet the wing feathers flex to give lifting power, wing curvature on whichever surface is facing up! So every wingbeat, whether going forward or backward, gives the lift that lets it hover motionless to sip nectar from flowers. Or just to hang in the air to gaze curiously at you.
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