The U.S. Department of Defense is grappling with significant delays and rising costs associated with the modernization of the F-35 Joint Strike Fighter’s Block 4 program, now not projected to reach completion until at least 2031, according to a newly released report from the Government Accountability Office (GAO). This Block 4 upgrade is intended to bolster the fighter jet’s operational capabilities, incorporating advanced weapons systems, enhanced sensors, and improved electronic warfare technologies to ensure effectiveness against evolving air defense strategies.
However, the GAO has identified multiple challenges hindering the program, including escalating expenses, technical difficulties, and production hold-ups. “Block 4 costs are over $6 billion more and completion is at least five years later than original estimates,” the report noted. As a result, the program is reportedly planning to trim the scope of Block 4 to deliver key capabilities at a more manageable pace.
In light of ongoing issues, the F-35 Joint Program Office is undergoing an organizational restructuring of Block 4, along with its Technology Refresh 3 (TR-3) upgrades, into a newly formed subprogram. This reorganization was mandated by Congress in 2023 to enhance oversight following successive delays in the program’s schedule. The TR-3 component, a $1.9 billion suite essential for enabling Block 4 features, has been the primary reason behind the delayed delivery of aircraft. In the past year, Lockheed Martin was able to deliver 110 F-35s, but these deliveries were behind schedule by an average of 238 days, as reported by the GAO.
Pentagon officials anticipate that planning documents will be finalized by the fall of 2025, which will clarify how many of the originally proposed 66 Block 4 capabilities will actually be retained in the restructured program. The GAO warns, however, that this reorganization may result in limitations to capabilities and uncertain costs will persist until a comprehensive estimate is finalized.
Additional complications stem from delays in the Pratt & Whitney F135 engine upgrade, which is essential for some future Block 4 capabilities and is not expected to enter production until 2031. Consequently, any capabilities reliant on this engine upgrade have been postponed to at least 2033. While the GAO reassured that the Block 4 subprogram will not directly depend on the engine upgrade, delays in that area could still affect future capability deliveries post-Block 4.
With costs associated with Block 4 previously estimated at $16.5 billion in 2021, the GAO indicates that a revised cost forecast will not be available until later this year. The report also criticized the management of contractor incentive fees, highlighting that bonuses were still awarded despite ongoing delivery failures. “The F-35 program’s use of incentive fees has been largely ineffective at holding the contractors accountable,” the GAO remarked.
The entire F-35 initiative, encompassing Block 4 modernization, the F135 engine upgrade, and the maintenance of a fleet exceeding 2,400 aircraft, is projected to exceed $2 trillion across its anticipated 77-year lifespan. To mitigate ongoing issues, the GAO has recommended that the Pentagon reevaluate delivery timelines, reconsider its incentive payment structures, and broaden the application of contemporary design methodologies, such as digital modeling. The defense agency has acknowledged four out of the six recommendations and has partially agreed to two of them.
