This book is intended to provide a description on the principles of aircraft flight in physical rather than mathematical terms. The authors have included some of the more important practical aspects of aircraft flight plus examples of innovations, descriptions of which are generally only found scattered in assorted technical journals. Although it contains no mathematical analysis, the authors do included one or two simple formulae as a means of defining important terms such as "lift coefficient" and Reynolds number, which are essential to the understanding of aeronautics. The authors have concentrated on items that they consider to be either important, or interesting. They have also restricted coverage to the aerodynamics and mechanics of flight, with only a brief consideration of other aspects such as structural influences. The book is intended primarily as a general introduction for anyone interested in aircraft or contemplating a career in aeronautics. Students of aeronautical engineering should find it helpful as introductory and background reading. It should also be useful to employees in the industry such as flight crew and ground staff. It is assumed that the reader has some school background in elementary physical science and is at least vaguely familiar with concepts such as energy and momentum.