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

Particular honour belongs to those who believed in the possibility of mechanical flight when all the world was against them; not the visionaries because they hoped for it merely, but those who by sheer force of intellect perceived the means by which it could be accomplished and directed their experiments along the right path. ... The name of Lilienthal is now among the most honoured, but curiously his own countrymen were the last to recognize the value of his work.

No one can realize how substantial the air is, until he feels its supporting power beneath him. It inspires confidence at once.

Artificial flight may be defined as that form of aviation in which a man flies at will in any direction by means of an apparatus attached to his body, the use of which requires personal skill. Artificial flight by a single individual is the proper beginning for all species of artificial flight, as the necessary conditions can most easily be fulfilled when man flies individually.

We returned home, after these experiments, with the conviction that sailing flight was not the exclusive prerogative of birds.

Small sacrifices must be made.

Of all the men who attacked the flying problem in the 19th century, Otto Lilienthal was easily the most important. ... It is true that attempts at gliding had been made hundreds of years before him, and that in the nineteenth century, Cayley, Spencer, Wenham, Mouillard, and many others were reported to have made feeble attempts to glide, but their failures were so complete that nothing of value resulted.