This part introduction presents an overview of the key concepts discussed in the subsequent chapters. The part explores professional training practices of air traffic control, pilots, and cabin crew and maintenance engineers, along with narratives from training experts in each area. Competency based education (CBE) is being implemented into a variety of professional areas in aviation. An effort has been made to remain neutral and avoid issues of rivalry that sometimes occur among professional groups in aviation. Most aviation training experts are intimately familiar with how professionals learn their trade, maintain skills throughout a career and acquire new expertise to move to greater levels of responsibility within their profession. To better understand CBE in aviation, it is important to understand how traditional training is conducted within professional disciplines, how CBE began in each role and what CBE looks like in present-day training. This understanding is crucial before one can consider how CBE might reshape future training practices.