Over the years, the National Transportation Safety Board (NTSB), Federal Aviation Administration (FAA), and other safety organizations have committed extraordinary resources to prevent civilian aviation accidents. Still, accidents can happen, often repeating the same sequence of events played out many times before. As a result, we are often left with the regrettable truth that there are really very few “new” accidents, just different players. So if there really are few “new” accidents, why has the aviation accident rate remained relatively stable over the last several years? What remains to be addressed is the small fraction of accidents attributable to perhaps the most complex problem facing aviation today - human error. According to FAA statistics, 70∼80% of aviation mishaps are at least partially attributable to human error. According to a study conducted by NTSB, accidents do not happen a single factor but multiple factors, which are in turn connected by 7 or more links-many of which are related to small human errors versus one big mistake. The purpose of this study is to discuss errors relating to the performance of Checklists/Procedures (one of the items related to the human error) and to discuss possible countermeasure for improvements.