I'm not aware of people trying to make flying machines that flapped their wings being a main blocker to powered flight. Gliders have been in development for hun

I'm not aware of people trying to make flying machines that flapped their wings being a main blocker to powered flight. Gliders have been in development for hundreds of years and were functioning decades before powered flight. The main blockers as I understand it were weight of the engine and the implementation of control surfaces. In fact, the first powered flight was done with a plane that mimicked the way a bird's control surfaces work.