WASHINGTON — The Pentagon now anticipates the F-35’s Block 4 modernization won’t be complete until 2031 at the earliest, a five-year delay from its original timeline, even as the department rescopes the effort to include fewer capabilities than originally envisioned, according to a new report by a congressional watchdog.
The latest estimate, published in a Government Accountability Office report today, is two years later than the last published projection of 2029 in May 2024.
The F-35 Joint Program Office is currently reorganizing the F-35’s Block 4 modernization and Technology Refresh 3 into a new subprogram due to a 2023 congressional mandate, which sought to improve execution of those efforts in light of continued cost increases and schedule delays. (Technology Refresh 3 includes a package of hardware and software upgrades necessary to support Block 4, which include upgrades to weapons, communications equipment and electronic warfare systems, among other technologies.)
“According to program officials, the new Block 4 major subprogram will have fewer capabilities, will experience schedule delays, and will have unknown costs until the program office finishes developing its cost estimate,” the GAO stated. “The program expects to finalize the acquisition planning documents establishing the Block 4 major subprogram in the fall of 2025,” which will cement which of the original 66 Block 4 capabilities will remain part of the subprogram.
While the program office told the GAO it could not lay out exactly which technologies would be part of Block 4, any change that would rely on a separate upgrade to the F-35’s engine and power management system will be deferred to a later date, as the F135 engine core upgrade will not be in production until at least 2031.
“While the Block 4 subprogram will not be dependent on upgrading the engine, engine core upgrade delays would likely contribute to more delays with delivering post–Block 4 capabilities,” the GAO said. “In May 2024, we reported that post–Block 4 capabilities and mission systems that the program expected to deliver in 2029 would need the new engine upgrades. Since then, the program revised its time frames for delivering those post–Block 4 capabilities that are dependent on these upgrades to 2033.”
An updated cost estimate for the Block 4 effort, which was $16.5 billion as of 2021, is expected “later in 2025,” according to the GAO.
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The GAO was broadly optimistic about the outlook for the Block 4 subprogram, writing that it would enable the Defense Department to have “improved insight” into cost, schedule and performance and to “make more informed decisions.”
F-35 prime contractor Lockheed Martin said the company intends to deliver at least 170 F-35s in 2025 and will continue fielding Block 4 capabilities “to ensure the F-35 maintains its unmatched dominance in the skies.”
The Defense Department, JPO and F-35 engine maker Pratt & Whitney did not immediately respond to a request for comment.
Continued Aircraft And Engine Delivery Delays
On the production side of the program, Lockheed and Pratt & Whitney have continued to struggle to deliver the F-35 aircraft and F135 engine on time — even as both contractors continued to make money on incentive fees linked, in part, to on time deliveries, in what the GAO called a “reward [to] contractors for delivering engines and aircraft late.”
All of the 110 jets Lockheed delivered in 2024 were handed over after the projected due date, largely because of delays to TR-3, the GAO said. Meanwhile, Pratt & Whitney delivered all 123 engines late in 2024, predominantly due to production and supply chain issues, although the delivery delays did not impact aircraft production.
The GAO recommended that the Defense Department should reevaluate its use of incentive fees in future contracts to ensure they actually result in performance gains, stating that the structure of the Lot 12-14 contract allowed Lockheed to deliver aircraft up to 60 days late while still earning some of the fee.
“The F-35 program’s use of incentive fees has largely been ineffective at holding the contractors accountable to delivering engines and aircraft on time,” the GAO stated. “For lot 15 aircraft, where the program originally tied incentives to on-time delivery, the program gave the contractor a second chance to earn fees by redirecting those incentives to other aspects of the program when it was clear that Lockheed Martin would not deliver any aircraft on time.”