Eleven inspectors from regional airlines participated in a study on inspection performance conducted at the FAA's Airworthiness Assurance NDI Validation Center (AANC) at Sandia Laboratories. These inspectors were asked to perform six inspection tasks, typical of inspections performed in their airline's maintenance department, on a testbed aircraft using workcards developed by the researchers. Performance on these six tasks varied widely between inspectors. Differences in performance were due to three main factors: differences in the domain knowledge of the inspectors, differences in workcard familiarity, and differences in the way the tasks were approached. The major factor seemed to be the individual's approach to the tasks.