The US Department of Defense is struggling to keep track of F-35 stealth fighter parts, according to a new government watchdog report.
The F-35 Lightning II Joint Strike Fighter program, the most expensive weapon system program in history, has faced consistent challenges with spare parts on top of rising acquisition and sustainment costs and readiness issues.
On Monday, the Government Accountability Office, a congressional watchdog agency, said that as of March 2026, due to a failure to maintain parts records at contractor-managed facilities, the F-35 Joint Program Office still didn’t know the status of over 1 million F-35 parts worth over $85 million that the GAO had flagged in 2023.
The report said the program office could not determine whether more recently reported losses included any of those previously identified.
The GAO found several pervasive problems that make it difficult for the JPO to account for F-35 parts.
And the program’s Enterprise Logistics Management System is at the center of those problems, the GAO found. The ELMS hasn’t been reliable because it pulls in data from a mix of sources and isn’t updated to reflect real-time changes and statuses. The GAO said that the issue is an inability to connect directly to prime contractor systems.
The Pentagon also lacks complete records for some parts. For example, the GAO found that as of March 2026, the program had not entered into its official system that roughly 17,000 parts, with a total value of about $1.3 billion, were undergoing maintenance or repair. Officials told the GAO the value could be as high as $2.5 billion when accounting for other costs such as transportation and overhead.
“The data are not reliable for asset accountability or financial reporting,” the GAO report said of information in the ELMS. “Timely and accurate data on F-35 parts are also important to ensure that the F-35 program is positioned to meet the needs of the warfighter.”
The Pentagon owns roughly 26 million F-35 parts worth an estimated $31 billion, and these are spread across over 700 government- and contractor-managed facilities.
Government-managed facilities hold about 70% of parts, while contractors store the remaining 30%, complicating the inventory process.
Since 2020, the F-35 Joint Program Office has spent at least $17 million conducting physical inventories of parts at contractor-managed and government-managed facilities, but the GAO found that these efforts have not adequately resolved issues.
“Until the interfaces with contractors’ systems are established and effective validation procedures to ensure data quality are implemented, DoD will not have accurate information about where its F-35 parts are located, what their value is, and how many there are,” the report said.
DoD concurred with recommendations from the GAO report. A JPO spokesperson told Business Insider that the department is implementing specific actions to monitor and analyze loss trends. “The JPO is actively developing program-specific procedures and tailored training for Accountable Property Officers (APOs), alongside a detailed plan to define and structure the APO program,” the spokesperson said.
The GAO regularly assesses aspects of the F-35 program.
Earlier this year, the watchdog reported that the mission-capable rate for the aircraft, or the amount of time that it’s available to perform one mission, fell from 67% to 44% between fiscal years 2021 and 2025. This has been a persistent concern for the program.
The full mission-capable rate, or the percentage of time that the F-35 can perform all its missions, declined from 38% to 25% during that same window. The F-35 is built for a broad set of missions, including air-to-air combat, ground attack, surveillance, and electronic warfare.
The US military operates three versions of the F-35 stealth fighter: the F-35As, built for conventional runways; the F-35Bs, which can take off from shorter runways and land vertically; and the F-35Cs, designed for aircraft carrier operations.
The GAO identified a lack of spare parts as one of the causes of the decrease in readiness, alongside maintenance issues. The Department of Defense launched a $13.7 billion readiness plan last year aimed at improving aircraft availability by the end of the decade. That investment could end up costing more than expected though.
The latest GAO report on the F-35 program warned that unreliable inventory records could make it difficult to determine which parts the program needs and in what quantities.
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