To become an airline pilot, a Commercial Pilot License (CPL) is required to start working professionally, usually as a first officer, while an Airline Transport Pilot License (ATPL) is needed to become a captain. The CPL allows pilots to fly for hire after completing required training and flight hours, whereas the ATPL requires higher experience (around 1,500 hours) and grants full command authority. Pilots typically begin with a CPL and then progress to an ATPL as they gain experience. This progression defines their responsibilities, seniority, and career growth in the aviation industry.