It is, I think, perhaps a remarkable thing that, unlike many inventions which require a general move forward over a wide field of achievement, at least one kind of flying, gliding and soaring, might have been achieved at any time in the past few thousand years. When, at the end of the last century, practical attempts were made it became apparent that effective control of heavier-than-air flying machines was a necessary requirement for its further progress. This was the problem that the Wright Brothers solved and made possible the development of aeroplanes.