That uncertainty matters as the Pentagon plans about $13.7 billion in additional spending to improve F-35 sustainment. GAO said the department could struggle to determine which parts to buy and in what quantities for a fleet whose U.S. and international operators draw from a shared pool.
As of March 2026, about 17,000 parts in maintenance or repair were absent from the Pentagon’s official property records. Those parts were valued at about $1.3 billion, though Pentagon officials said the figure could reach $2.5 billion once missing costs, transportation and overhead were included.
The F-35 Joint Program Office relies on data from prime contractors Lockheed Martin and Pratt & Whitney. As of August, the Pentagon’s system had no direct link to either contractor’s property system, and quarterly submissions meant records for the shared spares pool could be more than three months out of date.
The program office has spent at least $17 million on physical inventories since fiscal 2020, but its fiscal 2025 count still fell short of verifying which parts were on hand and whether the records captured them all. The Pentagon and its prime contractors did not know where some lower-tier suppliers were holding F-35 parts, and the Defense Contract Audit Agency was aiming to complete its first full count by March 2027.
GAO first reported in 2023 that one prime contractor had recorded losses involving more than a million parts valued at more than $85 million. By March 2026, the contractor had submitted about $28 million in losses for review, covering a wider period, but the program office could not tell whether that total included any of the losses GAO had previously identified.
The Defense Contract Management Agency determined that the contractor should be held liable for about $6 million of the $28 million. At government-managed facilities, 24 cases were reported more than a year after the losses were discovered, despite a 30-day reporting requirement.
The problems extend to the Pentagon’s financial statements. Department auditors have flagged a material weakness related to the F-35 program since fiscal 2019, and they found that leaving certain parts out of the fiscal 2025 accounts resulted in a material misstatement they could not quantify.
The Pentagon has until December 31, 2028, to obtain a clean audit opinion under federal law. It is reviewing how to value parts with missing or erroneous cost data and agreed to all four GAO recommendations, which call for closer monitoring of losses and a staffing plan, procedures and training for the officers responsible for tracking the parts.
Source: U.S. Government Accountability Office, GAO-27-108713, November 9, 2026.
