IN Brief:
- GAO found F-35 mission capable rates fell from 67% to 44% between fiscal 2021 and fiscal 2025.
- Full mission capable rates fell from 38% to 25% across the same period.
- The Global Support Solution Reset requires an estimated $13.7bn more than previously planned through fiscal 2031.
The F-35 programme’s sustainment challenge has become an industrial capacity problem, with declining availability rates exposing pressure across spare parts, maintenance, contractor incentives, and long-term affordability.
A new GAO assessment found that F-35 mission capable rates fell from 67% to 44% between fiscal 2021 and fiscal 2025, while full mission capable rates fell from 38% to 25%. The aircraft remains the US Department of Defense’s most costly weapon system, with US lifetime sustainment costs estimated at $1.6tn as of 2024 and more than 800 US aircraft already in operation.
The Joint Program Office has updated its sustainment approach through the Global Support Solution Reset, which requires an estimated $13.7bn more than previously planned through fiscal 2031. The reset is intended to address known weaknesses, including spare-parts shortages and heavy reliance on contractors. GAO found that the plan remains exposed to multiple risks, including the need for the private sector to deliver more than $7bn in additional parts and material.
For manufacturers and suppliers, the report reinforces a direct point: fifth-generation air power depends on an industrial base that can keep aircraft flying after delivery. Airframe production, final assembly, and headline acquisition numbers are only the visible part of the programme. The harder long-term work sits in canopies, coatings, actuators, sensors, engines, landing gear, diagnostics, software loads, depot capacity, and repair turnaround.
The F-35’s complexity increases that burden. A low-observable aircraft requires specialist maintenance, controlled materials, and careful management of surface treatments. Its mission systems, sensors, and software are central to capability, but they create configuration and update demands that differ from legacy fleets. When availability falls, the problem is rarely one failed component. It is usually a network of spares, repair queues, technical data, supplier bottlenecks, and maintenance manpower.
The sustainment reset’s dependence on private-sector capacity is critical. If key suppliers cannot produce enough parts, expand repair throughput, or qualify alternative sources, readiness goals will be difficult to reach regardless of funding. Defence ministries are asking suppliers to surge output, but aerospace supply chains are still affected by specialist labour shortages, long-lead materials, testing constraints, and competition from civil aviation.
Contract incentives also shape fleet availability. GAO found that past arrangements did not achieve F-35 readiness goals, partly because performance thresholds did not align with service requirements. Sustainment contracts direct behaviour across the support base. If incentives reward activity that does not improve operational availability, suppliers can meet contract terms while operators still face grounded aircraft.
The problem extends beyond the US fleet. F-35 operators across Europe and Asia-Pacific depend on the same global sustainment ecosystem. UK readers will recognise the issue from earlier scrutiny of the British F-35 fleet, where spare parts, engineering capacity, and infrastructure all affected availability. Allied missile development around new AMRAAM variants shows the same pattern at the weapons layer: common fleets create shared production, sustainment, and stockpile pressures.
The F-35’s export success adds to the challenge. More users mean a larger operational fleet, more national requirements, and greater total demand for spares. Scale should create efficiencies, but only if the supply chain is designed and funded to support it. If production and repair capacity lag behind fleet growth, international adoption can deepen the sustainment problem.
Software adds another layer. Aircraft availability is no longer defined only by mechanical condition. Mission-system updates, cybersecurity, configuration compatibility, and diagnostic data all influence readiness. A jet may be physically serviceable but still constrained by software, mission data, or configuration issues. That places software teams and digital infrastructure inside the sustainment enterprise.
The affordability gap is also widening. GAO noted that US military services could face more than a $1bn annual gap between projected F-35 sustainment costs and affordability goals by the mid-2030s. That gap will force choices around flying hours, fleet size, upgrades, depot investment, and contractor support. It may also influence future platform debates as air forces weigh crewed fighters against uncrewed collaborative aircraft and cheaper strike systems.
The F-35 remains central to US and allied combat air plans. Its sensor fusion, survivability, and weapons integration make it a cornerstone platform. The latest sustainment findings show that capability is being constrained by the industrial system behind it. The next phase of the programme will be judged not only by deliveries, upgrades, or new variants, but by whether suppliers, depots, and contracting structures can turn a growing fleet into available aircraft.
