Maintenance, repair and overhaul commonly refers to the activities used to inspect, service, diagnose, repair, modify, and restore equipment or assets so they can return to an intended operational condition. In manufacturing and industrial contexts, the term is most often used for complex, high-value assets such as aircraft, engines, rotating equipment, tools, or fielded systems that require controlled work, parts traceability, and documented service history.
MRO can describe both the work itself and the business or software processes that support it. These processes often include work order control, teardown and inspection, fault findings, parts consumption, replacement or repair decisions, testing, return-to-service records, and maintenance history. In regulated environments, MRO workflows commonly depend on accurate configuration data, serial or lot traceability, controlled instructions, and links between maintenance records and enterprise systems such as ERP, MES, EAM, or specialized MRO software.
The term should not be confused with routine production operations or with indirect MRO supplies, which refers to consumables and spare items used to support maintenance. In aerospace especially, MRO usually means sustainment work performed after an asset enters service, rather than original manufacturing, even though similar quality and traceability controls may apply.