The contrivances which are necessary to counteract the wind effects can only be understood by actual practice in the wind. - Otto Lilienthal

All flight is based upon producing air pressure, all flight energy consists in overcoming air pressure.

Experience alone can teach us the best forms of construction for sailing apparatus in order that they may be of sufficient strength, very light, and most easily managed.

I, too, have made it a lifelong task of mine to add a cultural element to my work, which should result in uniting countries and reconciling their people. Our experience of today's civilisation suffers from the fact that it only happens on the surface of the earth. We have invented barricades between our countries, custom regulations and constraints and complicated traffic laws and these are only possible because we are not in control of the 'kingdom of the air', and not as 'free as a bird'.
Numerous technicians in every state are doing their utmost to achieve the dream of free, unlimited flight and it is precisely here where changes can be made which would have a radical effect on our whole way of life. The borders between countries would lose their significance, because they could not be closed off from each other. Linguistic differences would disappear, as human mobility increased. National defence would cease to devour the best resources of nations as it would become impossible in itself. And the necessity of resolving disagreements among nations in some other way than by bloody battles would, in its turn, lead us to eternal peace. We are getting closer to this goal. When we will reach it, I do not know.