This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book discusses the topic of fatigue/alertness management in non-technical language. It concerns about the problem of fatigue in aviation and other settings. The book identifies some of the primary factors that cause fatigue in the workplace. It offers information on fatigue countermeasures that can be implemented in ground-based and in-flight aerospace operations. The global economy, social factors, and technological advancements have made the issue of aircrew fatigue more important now than ever before in the civilian aviation community. Meanwhile, the military aviation community has also extended the timing, range, and duration of flight missions to unprecedented levels. In civilian aviation, Gander found that one sample of pilots involved in short-haul trips worked an average of 10.6 hours per day, while another sample of long-haul pilots worked an average of 9.8 hours per day.