GAO: Lockheed Martin F-35 ‘overpromises and underdelivers’ as delays balloon to 238 days
September 5, 2025
The Pentagon’s most ambitious aircraft programme was supposed to be a cornerstone of US air dominance for decades. Instead, nearly 20 years after production began, the Lockheed Martin F-35 Joint Strike Fighter is billions over budget, years behind schedule, and still struggling to deliver aircraft that meet basic requirements.
That is the sobering conclusion of a new Government Accountability Office (GAO) report to Congress, which details how the programme continues to falter despite repeated course corrections and record levels of taxpayer spending.
“The F-35 programme continues to overpromise and underdeliver,” the watchdog warns, citing chronic delays, quality lapses, and incentive structures that reward failure more than performance.
F-35 costs balloon past $2 trillion as delays mount
When the Department of Defense (DoD) launched the F-35 programme in 2001, it projected acquisition costs of $233 billion. By 2012, that figure had risen to $396 billion after breaching statutory thresholds for overruns.
Today, acquisition costs stand at $485 billion, with lifetime sustainment projected at $1.58 trillion. Altogether, the fighter’s 77-year lifecycle will cost more than $2 trillion, making it the most expensive weapons programme in history.
Schedules have slipped repeatedly. The Pentagon originally promised to deliver 66 new Block 4 capabilities by 2026. By 2018, the date had shifted to 2029. Now, the GAO says even a reduced set of upgrades will not be complete until at least 2031, with some features pushed into the mid-2030s.
Technology Refresh 3 delays cripple Block 4 modernisation
The modernisation drive, known as Block 4, depends on a package called Technology Refresh 3 (TR-3). Valued at $1.9 billion, TR-3 includes upgraded processors, memory, and sensor systems meant to power new weapons, radar, and electronic warfare capabilities.
Instead, TR-3 has become a choke point. Hardware design was immature, deliveries were late, and software testing uncovered persistent stability issues — from radar malfunctions to cockpit display failures.
As a result, Lockheed Martin delivered 110 aircraft in 2024, every one of them late by an average of 238 days, nearly four times worse than 2023. Pratt & Whitney also delivered all 123 engines late, with average delays of 155 days.
By mid-2025, more than 100 jets were parked at Lockheed facilities awaiting fixes. To prevent production lines from becoming clogged, the Pentagon began “provisionally accepting” non-combat-capable jets. These aircraft, fitted with TR-3 hardware but incomplete software, are being used for training until upgrades are ready.
Supply chain shortages continue to slow F-35 production
Beyond TR-3, the programme has been hobbled by chronic supply chain shortages. As of early 2025, Lockheed reported more than 4,000 missing parts in its final assembly line, double historic levels.
In February 2025 alone, 52 aircraft sat idle at the final stage, awaiting components such as wing flaps. More than 1,600 of the shortages were directly tied to TR-3 hardware.
The Defence Contract Management Agency has issued multiple corrective action requests to both Lockheed and Pratt & Whitney. Yet shortages continue to affect not only new production but also the supply of spares needed to keep the fleet flying.
Lockheed Martin and Pratt & Whitney incentives under scrutiny
The GAO’s most scathing findings centre on how contracts are structured. Between 2021 and 2024, Lockheed Martin collected hundreds of millions of dollars in performance bonuses even as delays worsened. Contracts allowed partial fees for jets delivered up to 60 days late.
When no jets arrived on time, officials simply reprogrammed more than $100 million in unearned incentives to cover lab upgrades and TR-3 repairs.
Pratt & Whitney also benefited. Its incentive structure awarded tens of millions for meeting quality and assembly time targets despite universal late delivery. Penalties shaved off about $10 million, but strong performance in other categories offset the deductions.
“The use of incentive fees has largely been ineffective at holding contractors accountable,” the GAO concluded, warning the current system risks embedding a culture of missed deadlines without consequence.
Defects and variance requests weaken F-35 fleet readiness
Even when aircraft do arrive, many do not fully meet contract specifications. Lockheed has averaged around 40 “major variance requests” (MVRs) per jet since 2018.
These allow delivery of planes with known deficiencies ranging from premature part failures to corrosion and structural cracks.
Some defects have remained unresolved for more than 15 years.
As of March 2025, 475 out of 830 unique MVRs were still open. In June, the Pentagon requested $283 million to fix a subset of outstanding issues.
Pratt & Whitney faces similar problems, with seven engine variances logged in 2024 alone.
This latest report is not the first warning. Since 2001, the GAO has issued 53 recommendations to improve the F-35 programme; the DoD has acted on just over half.
Earlier reports flagged the dangers of building jets while still designing them, leading to costly concurrency issues. Others warned of rising sustainment costs and inadequate power and cooling planning, problems first identified in 2008.
Time and again, schedules and budgets have been revised, only to overshoot them again. Congress mandated a restructuring in 2012 and required regular GAO reviews from 2020. Yet the same issues remain: late deliveries, incomplete capabilities and spiralling costs.
UK F-35 upgrades delayed as Block 4 integration slips
Block 4 is critical for integrating new weapons, electronic warfare improvements and enhanced sensors.
For the UK, this directly impacts the integration of the SPEAR 3 precision weapon and Meteor beyond-visual-range missile. Without these upgrades, the Royal Air Force’s F-35B fleet remains reliant on a narrow set of US-approved munitions, limiting operational flexibility.
Analysts at Navy Lookout note that Britain is getting “something of a raw deal” from US industry and suggest the UK and other international customers should press the Joint Program Office for better performance or cost reductions when targets are missed.
The GAO also urges stricter contract terms, ending the practice of paying bonuses for late work, and greater transparency on production defects — costs that ultimately affect all partners.
Lessons from the F-35 should inform the UK’s next-generation fighter effort, GCAP, where adopting modern acquisition methods could avoid similar pitfalls.
GAO issues six recommendations to fix the F-35 programme
To break the cycle, the GAO has issued six new recommendations:
- Assess Lockheed Martin’s true capacity before raising production rates
- Redesign incentive structures to reward timely delivery
- Expand the use of digital tools such as “digital twins” to accelerate testing
- Formalise best industry practices in acquisition planning
- Build a comprehensive system to track and close variance requests
- Use modern acquisition pathways for engine modernisation to ensure oversight
The DoD agreed with four and partially concurred with two.
Lockheed Martin defends the F-35 as ‘combat proven’
Lockheed Martin pushed back, noting that 2024 was an atypical year because deliveries were paused until July.
“The F-35 is combat-proven, offers the most advanced capability and technology, and is the most affordable option to ensure America and its allies remain ahead of emerging threats,” a company spokesperson told AGN.
The contractor expects to deliver between 170 and 190 aircraft in 2025 while continuing to field Block 4 capabilities “to ensure the F-35 maintains its unmatched dominance in the skies.”
The Pentagon plans to buy 2,470 F-35s to replace ageing fleets across the Air Force, Navy and Marine Corps. More than 1,100 are already in service, and partner nations from Britain to Japan rely on the aircraft for their own defence.
Yet the GAO warns that without fundamental changes, the programme risks compounding delays while draining ever more resources.
After two decades, hundreds of billions in overruns and promises deferred, the F-35 remains both the cornerstone of allied airpower and the Pentagon’s most costly cautionary tale.
