Select Committee · Public Accounts Committee

The UK’s F-35 stealth fighter capability

Status: Open Opened: 10 Jul 2025 7 recommendations 23 conclusions 1 report

The F-35 is a fifth-generation stealth fighter aircraft, which is able to enter contested environments undetected. As part of a US-led programme, the Ministry of Defence (MoD) purchased and is using the F-35b variant, which can operate from land and aircraft carriers. The UK publicly committed to purchasing 138 F-35 aircraft from the global F-35 …

Clear

Reports

1 report
Title HC No. Published Items Response
51st Report - The UK’s F-35 stealth fighter capability HC 1232 31 Oct 2025 30 Responded

Recommendations & Conclusions

14 items
7 Conclusion 51st Report - The UK’s F-35 stealth fig… Deferred

F-35 Full Operating Capability repeatedly delayed, with sustainability issues unresolved.

The Department expects to declare Full Operating Capability (FOC) by the end of 2025. In its 2018 Concept of Use document the Department had expected to declare FOC by the end of 2023 based on two frontline squadrons of 12 aircraft and a training squadron at full capacity. It subsequently …

Government response. The government response is entirely unrelated to the recommendation regarding the F-35 Full Operating Capability (FOC) declaration, instead discussing the 'illegal meat crisis' and biosecurity at the border.
HM Treasury
8 Conclusion 51st Report - The UK’s F-35 stealth fig… Deferred

F-35 Full Operating Capability declaration based on military judgement and factual assessment.

The Department told us that its criteria for declaring FOC are based on a combination of hard facts and applied military judgement. In forming its view, it told us that it had considered FOC through four distinct 5 C&AG’s Report, para 9 6 Q 91 7 C&AG’s Report, para 1.19 …

Government response. The government response is entirely unrelated to the recommendation regarding the F-35 Full Operating Capability (FOC) criteria, instead discussing animal vaccine availability and ongoing cross-sector engagement, with an action plan to be published in late 2026.
HM Treasury
9 Conclusion 51st Report - The UK’s F-35 stealth fig… Deferred

F-35 Full Operational Capability definition omits critical standoff weapon and personnel readiness

The Department acknowledged that its definition of FOC excludes a crucial element of capability. It does not include a requirement to integrate Spear 3 onto the F-35 to provide a standoff weapon to attack ground targets from a safe distance, which it does not expect to have until the early …

Government response. The government response is entirely unrelated to the recommendation regarding the F-35 FOC definition, Spear 3 integration, or personnel shortages, instead discussing Sanitary and Phytosanitary (SPS) agreements with the EU and strengthening resilience to animal disease.
HM Treasury
11 Recommendation 51st Report - The UK’s F-35 stealth fig… Deferred

Overall F-35 capability and availability remain inadequate, lacking standoff weapons and stealth assessment

Although the F-35 is significantly superior to any previous UK aircraft, the Department has yet to achieve the capability or availability that it wants.19 Most significant is the lack of the standoff weapon.20 This will limit the UK’s ability to conduct certain missions in contested environments.21 The Department also told …

Government response. The government will set out its approach to delivering the Strategic Defence Review and the investments required to deliver the Integrated Force in the forthcoming Defence Investment Plan, including details on the standoff capability requirement.
HM Treasury
12 Conclusion 51st Report - The UK’s F-35 stealth fig… Deferred

F-35 capability limitations result from global programme dependencies, supplier issues, and ASAF delays

The Department set out why these capability limitations have occurred. It told us that its ability to integrate new weapons was dependent on the global F-35 programme run by the United States Department of Defense. It requires the major software enhancements provided by Tech Refresh 3 and Block 4, which …

Government response. The government will set out its approach to delivering the Strategic Defence Review and the investments required to deliver the Integrated Force in the forthcoming Defence Investment Plan, including details on the standoff capability requirement.
HM Treasury
13 Recommendation 51st Report - The UK’s F-35 stealth fig… Deferred

Department actively pursuing solutions to F-35 limitations, accelerating weapon integration and international assessment

The Department told us that it had plans to tackle these limitations. It is seeking opportunities within the global programme to accelerate the integration onto the F-35 of Spear 3 and Meteor, its preferred air to air weapon. The Joint Programme Office, which runs the global programme, has invited the …

Government response. The government agrees with the Committee’s recommendation and states that the forthcoming Defence Investment Plan will set out the government’s approach to delivering the Strategic Defence Review (SDR) and the investments required to deliver the Integrated Force. This will provide …
HM Treasury
18 Recommendation 51st Report - The UK’s F-35 stealth fig… Deferred

F-35 personnel at RAF Marham face unacceptable, low-quality accommodation and insufficient amenities

RAF Marham has been designated the F-35 main operating base since 2013 and now has at least 1,500 people working at the base to support the F-35 fleet, many of whom also live there.38 A 2025 NISTA programme review found that most of the accommodation offered at RAF Marham was …

Government response. Following the publication of the Defence Investment Plan infrastructure requirements will be reassessed against departmental priorities. The department will write to the Committee by 31 May 2026 to advise whether the current timescale for RAF Marham accommodation can be brought …
HM Treasury
19 Conclusion 51st Report - The UK’s F-35 stealth fig… Deferred

Defence estate accommodation, particularly at RAF Marham, remains inadequate and outdated

The Department accepted that accommodation at RAF Marham is not good enough, reflecting wider problems within the Defence estate, more than half of which is over 50 years old. The Department told us that it had identified the need for increased investment in accommodation in the Strategic Defence Review and …

Government response. The government agrees with the recommendation, but will reassess infrastructure requirements against departmental priorities following the publication of the Defence Investment Plan and will advise the Committee by 31 May 2026 whether the current timescale for RAF Marham accommodation can …
HM Treasury
20 Conclusion 51st Report - The UK’s F-35 stealth fig… Deferred

Poor quality accommodation significantly impacts defence personnel retention and engagement

The Department acknowledged that providing poor quality accommodation negatively impacts its personnel. Most significantly, it increases the risk that people leave the service earlier than they otherwise would.41 This is a serious risk given the problems with retention that the Department has set out and the length of time it …

Government response. The government agrees with the recommendation, but will reassess infrastructure requirements against departmental priorities following the publication of the Defence Investment Plan and will advise the Committee by 31 May 2026 whether the current timescale for RAF Marham accommodation can …
HM Treasury
21 Recommendation 51st Report - The UK’s F-35 stealth fig… Deferred

Accelerate the unacceptable 13-year accommodation upgrade programme at RAF Marham

The Department told us that it has plans to upgrade accommodation at RAF Marham but will not complete these plans for many years. The Department will upgrade 900 accommodation units and bedrooms across the base. However, the Department told us that the programme for doing so began in 2021 and …

Government response. The Department will reassess infrastructure requirements against departmental priorities following the publication of the Defence Investment Plan, and will advise the Committee by 31 May 2026 whether the timescale for RAF Marham accommodation can be brought forward.
HM Treasury
22 Conclusion 51st Report - The UK’s F-35 stealth fig… Deferred

Prioritisation of short-term affordability in F-35 programme led to higher long-term costs

The Department acknowledged that it has, on occasion, prioritised short-term affordability over value for money in the F-35 programme, to keep within its overall departmental budget.46 Notably, in 2021 the Department took the decision to delay investment in the Air Signature Assessment Facility (ASAF). Although this decision saved £82 million …

Government response. The government agrees with the Committee’s recommendation and states that as part of the production of the forthcoming Defence Investment Plan, the government is considering the long-term impacts of any savings measures on costs and capability of all major programmes.
HM Treasury
23 Conclusion 51st Report - The UK’s F-35 stealth fig… Deferred

Delaying 809 Naval Air Squadron infrastructure led to significantly increased construction costs

In correspondence provided after our evidence session the Department told us that 809 Naval Air Squadron’s infrastructure is another example of short-term savings resulting in higher overall costs. In 2020 the Department forecast that the cost of building the infrastructure would be around £56 million and be completed in 2023. …

Government response. The government agrees with the Committee’s recommendation and states that as part of the production of the forthcoming Defence Investment Plan, the government is considering the long-term impacts of any savings measures on costs and capability of all major programmes.
HM Treasury
24 Conclusion 51st Report - The UK’s F-35 stealth fig… Deferred

Short-term F-35 programme savings negatively impact defence capabilities and operational readiness

The Department also acknowledged that short-term savings impact the capability provided by the programme. The ASAF, which measures the stealth characteristics of the UK F-35 fleet, is needed for the Department’s freedom of action policy so that it can deploy the aircraft at any time or place of its choosing.49 …

Government response. The government agrees with the Committee’s recommendation and states that as part of the production of the forthcoming Defence Investment Plan, the government is considering the long-term impacts of any savings measures on costs and capability of all major programmes.
HM Treasury
25 Conclusion 51st Report - The UK’s F-35 stealth fig… Deferred

Delays in F-35 aircraft delivery reduced fleet numbers with marginal cost impact

The Department told us that in 2010, facing a reduction in its budget, it chose to delay the delivery of some aircraft.52 This has reduced the number of aircraft available to the Department today.53 This was exacerbated by a further delay of seven aircraft by a year in 2020 for …

Government response. The government is considering the long-term impacts of savings measures on costs and capability of all major programmes as part of the production of the forthcoming Defence Investment Plan.
HM Treasury

Oral evidence sessions

1 session
Date Witnesses
8 Sep 2025 Air Chief Marshal Sir Richard Knighton KCB · Ministry of Defence, Air Commodore Nick Lowe · Ministry of Defence, David Williams · Daily Mail, Dominic Wilson · Ministry of Defence View ↗

Correspondence

4 letters
DateDirectionTitle
14 May 2026 To cttee Letter from the Permanent Secretary at the Ministry of Defence relating to The …
20 Apr 2026 To cttee Letter from the Permanent Secretary of the Ministry of Defence to the Chair of …
26 Mar 2026 From cttee Letter to the Permanent Secretary at the Ministry of Defence relating to Treasu…
16 Oct 2025 To cttee Letter from the Permanent Secretary of the Ministry of Defence relating to the …