In reviewing aircraft accidents, several assumptions were made. Paperwork was not properly completed after the shift, work cards were not used to document the work completed by the evening shift and the mechanics did not brief their supervisor. Aircraft maintenance engineers take an approved course to acquire the knowledge and basic skills to enter the profession. However, the aviation industry is dynamic: operators change their aircraft, new aircraft types and variants are introduced and new aircraft maintenance practices are introduced. As a result, the engineer must keep his knowledge and skills up-to-date.