Augmented Reality (AR) is a strong growing research topic in several areas including industry, training, art and entertainment. AR can help users to achieve very complex tasks by enhancing their vision with useful and well-adapted information. This paper deals with evaluating the usability of AR in aeronautic maintenance training tasks. A case study in the on-site maintenance department was conducted using an augmented reality application, involving operators at several levels of expertise. Obtained results highlighted the full efficacy of AR in the field of aeronautic maintenance.