This research has objective 1) to study factor of delay aircraft 2) to study factor of on time aircraft and 3) to compare between delay factor and on time factor aircraft. Research methodology: we use random sampling to department of flight planning in one Airline of Asia Region which has 8 staffs and tools in this research is semi - structured interview which was valid by data triangulation. The result found that the most delay factor is air traffic control, passenger/baggage and weather, and technical respectively. The most on time aircraft is teamwork and air traffic control, weather, passenger/baggage, readiness of aircraft, and ramp service respectively. When compare between factor we found that the same factor are passenger/baggage, air traffic control, and weather.