[YeGoblynQueenne]

>> (Insert the usual stuff like a plane being unable to fly like a bird or a submarine not swimming is totally irrelevant to it being useful).

Just a brief reminder that planes have wings with airfoils just like birds and submarines have air tanks just like fish have swimming bladders.

Some birds fly without flapping their wings much, too, e.g. albatrosses.

[balazstorok]

You are right in that. Propulsion is different in both cases. The point is, until you have not recreated the function, difficult to say which part is important in other implementations (~Marr levels).

Leonardo tried to create flapping wings.