The F-35 Lightning II, the most expensive weapons program in U.S. history, is falling short of the combat-readiness standards the Pentagon set for it. Federal audits through fiscal year 2024 show that every variant of the jet misses its minimum mission-capable targets by double-digit percentage points, while software delays and a broken spare-parts pipeline compound the problem. The gap between what the F-35 was supposed to deliver and what it actually provides on the flight line raises hard questions about whether the fleet can sustain prolonged operations in a serious conflict.
Mission-Capable Rates Keep Sliding
The Defense Department measures fighter readiness in two ways: mission-capable rates, which track whether an aircraft can perform at least one of its assigned missions, and full mission-capable rates, which measure whether it can perform all of them. A long-standing Government Accountability Office framework established these metrics as the key ingredients of aircraft availability strategy. By those measures, the F-35 is not where it needs to be. Through FY2024, all three F-35 variants missed their minimum-performance targets by percentage-point gaps that the GAO flagged as persistent, according to a recent readiness assessment of the fighter fleet.
The trend line is moving in the wrong direction. A separate GAO review found that overall F-35 availability has been declining even as sustainment costs rise, documenting how estimated life-cycle spending increased between 2018 and 2023 while the share of jets ready to fly fell. That combination, paying more for less readiness, signals a structural problem rather than a temporary dip. When availability drops, fewer jets are on the ramp ready to launch, which directly limits how many missions a combatant commander can schedule in a given day or week and constrains the ability to surge sorties in a crisis.
A Spare-Parts System Losing Track of Millions
One reason jets sit idle is that they are waiting for parts. The F-35 program relies on a global spares pool shared among the United States and its international partners, and that pool has serious accountability gaps. A GAO audit documented that roughly one million serialized components worth approximately $85 million had been lost or otherwise unaccounted for in the system. Only about 2% of those loss circumstances had been reviewed since 2018, meaning the program office had almost no visibility into why parts were disappearing, where they ended up, or whether underlying processes were being corrected.
The practical effect is straightforward: if a maintainer at an air base in Japan or Italy cannot get a turbine blade or an avionics card because the global pool cannot account for its inventory, that jet does not fly. The GAO identified governance and accountability failures in the spares pool as a root cause, pointing to weak oversight and incomplete records. Without reliable tracking, the program cannot predict shortages, cannot prevent theft or waste, and cannot prioritize shipments to the units that need them most. For a fleet that already misses readiness targets, every grounded jet waiting on a part widens the gap between the F-35’s promised capability and its actual output in day-to-day operations.
Software Delays Stall New Deliveries
The readiness problem does not stop at the jets already in service. New aircraft are arriving late and, in many cases, without the software needed to fight. All 110 F-35s delivered in 2024 were late, by an average of 238 days per aircraft, according to a GAO review of the Joint Strike Fighter program’s modernization schedule. The delays stem from the troubled rollout of Technology Refresh 3, or TR-3, the new hardware and software configuration that is supposed to enable future Block 4 capabilities such as upgraded sensors, electronic warfare improvements, and expanded weapons integration. Both TR-3 and Block 4 have experienced repeated schedule slips, pushing key combat enhancements further into the future.
Lockheed Martin acknowledged the bottleneck in a quarterly financial filing with the Securities and Exchange Commission, disclosing that customer deliveries of the fighter were halted in early 2024 pending TR-3 software finalization and validation. The GAO linked those late deliveries to non-combat-capable configurations and to incentive structures that may not adequately penalize schedule slips or incomplete capability. In plain terms, some jets rolled off the production line and were handed to the military in a state that required further upgrades before they could be used in combat. That means the Pentagon is accepting airframes it cannot immediately put on the mission board, which inflates the total fleet count on paper while doing little to improve actual readiness in the near term.
Data Rights Disputes Slow Repairs
Even when parts are available and software is current, the military faces another barrier: access to the technical data needed to fix the jets. The F-35 program depends heavily on contractor logistics support, and intellectual property restrictions can limit what military depots are allowed to repair on their own. A GAO examination of data rights planning across major systems, reissued with revisions, included the F-35 among programs facing sustainment challenges tied to limited access to engineering information. When the government does not own or control the necessary data, it must negotiate with the prime contractor for every new repair capability it wants depots to assume.
When depot maintainers lack the drawings, diagnostic software, or repair procedures they need, they must send work back to the original equipment manufacturer or wait for contractor teams to arrive, adding time and cost to every maintenance action. For a fleet already short on available jets, any delay in turning around a grounded aircraft has an outsized effect on the number of combat-ready planes at any given moment. The data rights issue also limits the Pentagon’s ability to introduce competitive repair contracts or diversify its industrial base, which could otherwise help drive down the sustainment costs that have been climbing steadily even as, according to a GAO sustainment review, the share of ready aircraft continues to lag behind goals.
What This Means for Sustained Combat Operations
Most public discussion about the F-35 focuses on its stealth profile, advanced sensors, and ability to share data across the battlespace. Those characteristics matter in a high-end fight, but they only translate into real combat power if enough jets are available to fly when needed. The GAO’s recent readiness analysis underscored that mission-capable rates across the fleet remain well below the thresholds the services set for themselves, and that these shortfalls have persisted despite years of corrective action plans. In a short, intense conflict, commanders might be able to mask some of these problems by surging maintenance crews and cannibalizing parts from grounded aircraft. Over weeks or months of sustained operations, however, the structural weaknesses in the F-35 enterprise (lost parts, software delays, and constrained repair capacity) would become harder to hide.
The implications go beyond a single weapons system. The Pentagon has built much of its future airpower strategy around the assumption that the F-35 will be available in large numbers, able to penetrate defended airspace and cue other forces. If only a fraction of the inventory can meet all of its assigned missions on any given day, that strategy becomes riskier. Fixing the problem will require more than incremental tweaks: the GAO’s findings point to the need for stronger oversight of the global spares pool, more realistic software schedules, and a more assertive approach to acquiring the technical data needed for organic repairs. Until those underlying issues are addressed, the world’s most expensive fighter risks being a fleet of hangar queens, highly capable on paper, but too often unavailable when it counts.
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*This article was researched with the help of AI, with human editors creating the final content.
