To study maintainer error, the Naval Safety Center’s Human Factors Accident Classification System (HFACS) was adapted for Maintenance Related Mishaps (MRMs). The HFACS Maintenance Extension (ME) successfully profiled the errors present Naval Aviation Class A MRMs. In order to assess its suitability for studying major and minor airline accidents, a post hoc analysis was conducted on 124 Naval Fleet Logistics Support (VR) Wing maintenance related mishap, hazard, and injury reports. Two judges separately coded the 124 VR Wing incidents; a Cohen’s kappa of .78 was achieved, indicating an “excellent” level of agreement. Generally, HFACS-ME was able to profile maintainer errors found in more minor incidents and the factors that contribute to them. Common factors observed include errors attributed to third party maintenance, inadequate supervision, failed communications, skill-based errors, and procedural violations.