Defence maintenance, repair and overhaul (MRO)—often expanded to maintenance, repair, overhaul and upgrade (MRO&U)—is the work that keeps military equipment serviceable and available for missions. The opportunity is not limited to repairing hardware: it also includes parts, technical data, depot capacity, trained maintainers, upgrades and maintenance analytics. But needs differ by platform and country, and policy priorities or spending figures do not prove that a particular contract is open to suppliers.
What defence MRO includes
MRO spans routine maintenance through deep repair, rebuild and upgrade. It is a connected support system: a repair may be delayed not because the equipment is beyond repair, but because a part is unavailable, technical drawings are out of date, or trained staff and depot capacity are insufficient.
- Field maintenance and repair: planned and unplanned work performed at unit, field or operational locations to restore serviceability.
- Depot repair and overhaul: deeper work on equipment or components. Depot capacity and decisions about which systems receive overhaul affect how much work can be completed.
- Parts and supply support: sourcing and managing repair parts and materiel, including parts recovered from equipment leaving service.
- Technical data and engineering: access to current data and drawings needed to diagnose faults and carry out repairs.
- Workforce: maintainers with the skills and training required for the platform and work being performed.
- Upgrade and integration: modifications and enhancements, alongside design, integration, manufacture and sustainment. Australia explicitly includes MRO&U in its defence-industrial priorities.
- Condition monitoring: sensors and data analytics that can inform when maintenance is needed, rather than relying only on fixed schedules.
- Regional sustainment: repair networks that place capability closer to operational need, including through allied, partner or industrial collaboration.
These capabilities apply across aircraft, ships, ground vehicles and other systems, but evidence about one fleet should not be treated as a finding about every domain. A 2024 GAO review described readiness challenges across air, sea, ground and space; it reported maintenance and supply issues limiting mission-ready aircraft availability and minimal progress modernizing Navy shipyards, drawing on prior work rather than providing a single measure of all MRO capacity. GAO-24-107463
Why MRO matters to readiness
Maintenance budgets alone do not ensure that equipment is available when needed. In its review of U.S. tactical aircraft, GAO found that mission-capable rates generally had not met Department of Defense goals for several years, citing aging aircraft, maintenance challenges and supply-support issues. The pattern differed by service: for the aircraft reviewed, Navy and Marine Corps rates rose over fiscal years 2018–2023, while the reviewed Air Force rates fell. Those findings apply to the aircraft in that review, not to every aircraft fleet. GAO-25-107870
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For 18 Army and Marine Corps ground vehicles selected for review, GAO found that all were affected by shortages of parts and materiel and a lack of current technical data or drawings. Other common problems included shortages of skilled maintainers, service-life issues and unplanned maintenance. Because the review covered selected vehicles, it is not a statistical census of all military ground platforms. GAO-25-108679
What the reported spending and overhaul figures show
The following figures describe specific U.S. services, systems and periods. They are not a global defence-MRO market estimate, and the spending totals do not establish the value of work available to any one supplier.
| Measure | Reported figure | Scope and qualification |
|---|---|---|
| Tactical-aircraft operation and sustainment spending | About $57.2 billion | U.S. Navy, Marine Corps and Air Force spending during FY2018–2023 for the tactical aircraft covered by GAO’s 2024 report; not total defence MRO spending. GAO-25-107870 |
| Army depot overhauls of selected ground vehicles | 1,278 in FY2015; 12 in FY2024 | Counts reported by GAO for selected vehicles; overhaul volume can reflect fleet and service decisions as well as capacity. GAO-25-108679 |
| Marine Corps depot overhauls of selected ground vehicles | 725 in FY2015; 163 in FY2024 | GAO notes some newer vehicles had not entered overhaul, while some vehicles being phased out had stopped receiving overhauls. GAO-25-108679 |
| Army and Marine Corps ground-vehicle depot maintenance spending | More than $2.3 billion combined in FY2023 | Spending for the services’ ground vehicles, not all defence sustainment. GAO-25-108679 |
| U.S. weapon-system maintenance | Nearly $90 billion annually | Figure presented in a 2022 GAO report’s discussion of U.S. Department of Defense maintenance; it is not a global market measure. GAO-23-105556 |
The figures are useful indicators of the scale and variation of selected sustainment activity, not like-for-like measures: they cover different populations, services and kinds of spending or work. Overhaul counts in particular should not be read as a simple measure of unmet demand, since fleets change and some vehicles may not yet be due for overhaul.
Where governments and suppliers may find opportunities
Regional repair networks
The U.S. Department of Defense’s 2024 Regional Sustainment Framework aims to build more MRO capability closer to operational need through partner nations, industrial partners and cooperative arrangements. It points toward regional depots, repair networks and allied industrial collaboration, but it does not identify a universally open procurement or guarantee that a specific country, platform or supplier has an opportunity. The announcement quotes Under Secretary of Defense for Acquisition and Sustainment Dr. William A. LaPlante describing the aim as delivering enhanced sustainment capability in theater through global partnerships. U.S. Department of Defense, May 15, 2024
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National industrial priorities
Australia’s Defence Industry Development Strategy names aircraft MRO&U, continuous naval shipbuilding and sustainment, and sustainment and enhancement of the combined-arms land system as Sovereign Defence Industrial Priorities. The strategy says Defence will work with industry to identify capability shortfalls, critical paths and growth areas. These are Australian policy priorities; they should not be assumed to match another country’s requirements. GAO-25-108679
Repair-ecosystem enablers
The documented bottlenecks suggest supplier categories that may be relevant to sustainment programs: repair parts and materiel, current technical data and drawings, skilled-maintainer training, depot overhaul capacity, and maintenance analytics. These are capability areas, not evidence that a named vendor, solicitation, enrollment route or contract is available.
How predictive maintenance fits—and where it does not
Predictive maintenance uses condition-monitoring technology and data analytics to schedule work based on evidence of need. In principle, that can help maintenance teams identify when an intervention is warranted instead of depending only on a fixed interval. GAO reported that the U.S. services had plans and metrics for implementation, while also emphasizing that suitability and implementation vary across weapon systems. It is a data-enabled capability, not a guaranteed readiness fix or a substitute for parts, technical data, skilled staff and repair capacity. GAO-23-105556
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How to assess a defence MRO opportunity
For a supplier or industry partner, the first question is not simply whether a defence budget is large. It is whether the capability matches a defined platform, location, repair need and procurement route. Compare offers or potential work against the following factors:
Best Value
- Platform and domain: identify the aircraft, vessel, vehicle or other system; do not transfer findings across domains without evidence.
- Location and network: determine whether the work is field or depot level, national or regional, and how close it needs to be to likely operational demand.
- Repair depth and throughput: distinguish routine maintenance, component repair, overhaul and upgrade; establish available work slots and demonstrated capacity.
- Supply and data access: verify parts availability, rights to technical data, data currency and supply-chain resilience.
- People and assurance: establish required skills, training, certification, safety and quality controls for the target system and jurisdiction. Specific requirements must be confirmed for the program.
- Performance measures: clarify how the customer measures availability or mission-capable rate, turnaround time, maintenance hours, cost and repeat failures. GAO reports service goals and predictive-maintenance metrics, but no universal benchmark for all systems.
- Sovereignty and partnership: understand how local control and resilience relate to allied or regional collaboration objectives; the balance is program- and country-specific.
These checks help distinguish a policy priority or broad spending figure from a defined opportunity with an eligible buyer, scope, procurement process and deliverable. The cited material supports category-level opportunity areas, but does not verify any particular open solicitation or supplier pathway.
What the evidence does not establish
The cited sources do not establish a comparable global defence-MRO market size or identify a fastest-growing country. U.S. maintenance spending should not be repurposed as a global market estimate, and Australian sovereign priorities are not universal policy. The UK Ministry of Defence and Defence Equipment & Support annual-report page confirms that its 2024–25 report covers the year ending March 31, 2025 and was published July 21, 2025; the landing page alone does not substantiate a specific MRO opportunity. UK Ministry of Defence and DE&S annual report and accounts 2024 to 2025
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