This chapter looks at how competencies are developed and written. The competencies are used for designing, facilitating and assessing learning. Occupations that use the Competency-based education (CBE) approach adapt and evolve their own ways of conceptualizing competent work, their own ways of analyzing it and their own ways of structuring competency texts. In Britain, Mansfield and Mathews created the "job competence model," which was explicitly oriented to CBE. The International Civil Aviation Organization (ICAO) model can be found in frameworks developed for a range of occupations in the aviation industry. The ICAO competencies for cabin crew therefore represent a hybrid model that covers behavioral and cognitive components of competence. Work done by the Flight Crew Licensing and Training Panel (FCLTP)on developing competencies for entry-level training and assessment for pilots produced several "competency units". The CBE approach has a complex relationship with the discipline of instructional systems design (ISD).