UK Inquiry Tracker

The UK’s F-35 stealth fighter capability

Public Accounts Committee Open Inquiry

Opened: 10 Jul 2025 Parliament page

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 … Read more 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 programme in 2006, and currently expects to have received 48 aircraft by the end of 2025. Of the eight international partners under US-led global programme, the UK has the biggest commitment to the F-35 outside of the US’ own services. The MoD estimates that the F-35 fleet will cost more than £18bn over its life. The PAC reported in June 2025 that defence scrutiny was being obstructed, with the unacceptable continuing lack of a Equipment Plan meaning that the public still lacked a reliable assessment of whether government’s defence spending plans were affordable. The PAC found in 2021 that the defence procurement system was “broken,” following which the MoD created the new role of National Armaments Director (NAD) as part of the biggest reforms in fifty years. In June 2025, the PAC led a House of Commons debate on the NAD’s remit. The National Audit Office (NAO) reports in 2025 on the UK’s F-35 aircraft programme, examining whether the MoD is delivering its F-35 capability aims in a way which maximises value for money. Following the NAO’s report, the PAC will take evidence from senior MoD officials and military leaders on subjects including current and future programme costs, MoD’s management of the UK’s participation in the global programme, and the resources in place to support the UK’s F-35 capability. As part of the session, the Committee will also question officials from the Ministry of Defence about the Afghanistan Response Route (ARR) and associated data breaches. The ARR was set up by the MoD to mitigate the security risks arising from a data protection breach and the unauthorised disclosure of personal information about Afghan citizens which occurred in February 2022. The National Audit Office (NAO) has published a report on the Afghanistan Response Route (ARR) to support the Committee’s scrutiny. If you have evidence on these issues, please submit it here by 23:59 on Monday 25 August 2025. Please look at the requirements for written evidence submissions and note that the Committee cannot accept material as evidence that is published elsewhere. You can request anonymity or confidentiality when you send evidence, but it is the Committee which decides what information to publish and how. It may treat submissions confidentially, even where you have not requested this. Please note that the Committee’s inquiry cannot assist with individual cases. If you need help with an individual problem you are having, you may wish to read the information on Parliament’s website about who you can contact with different issues . Show less

7 Recommendations

23 Conclusions

1 Report

1 Oral session

4 Letters

1 Event

Activity timeline 8 events

14 May
2026

Correspondence

Letter from the Permanent Secretary at the Ministry of Defence relating to The UK’s Stealth Fighter Capability (recommendations 2a ,2b, 4 a…

20 Apr
2026

Correspondence

Letter from the Permanent Secretary of the Ministry of Defence to the Chair of the Public Accounts Committee relating to The UK’s F-35 stea…

26 Mar
2026

Correspondence

Letter to the Permanent Secretary at the Ministry of Defence relating to Treasury Minute response – The UK’s F-35 stealth fighter capability

19 Jan
2026

Report published

Treasury minutes: Government response to the Committee of Public Accounts on the Fifty-first report from Session 2024-26

31 Oct
2025

Report published

51st Report - The UK’s F-35 stealth fighter capability

16 Oct
2025

Correspondence

Letter from the Permanent Secretary of the Ministry of Defence relating to the oral evidence session on 08 September 2025 on the UK’s F-35 …

8 Sep
2025

Oral evidence

Oral evidence session

8 Sep
2025

Formal meeting (oral evidence session) · Room 8, Palace of Westminster

Committee event

Oral evidence sessions 1 session

8 Sep 2025

View on parliament.uk

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

Reports 1 report · click to expand

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 results

7 Conclusion Deferred

51st Report - The UK’s F-35 stealt…

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 … Read more

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

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8 Conclusion Deferred

51st Report - The UK’s F-35 stealt…

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, … Read more

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

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9 Conclusion Deferred

51st Report - The UK’s F-35 stealt…

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, … Read more

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

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11 Recommendation Deferred

51st Report - The UK’s F-35 stealt…

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 … Read more

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

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12 Conclusion Deferred

51st Report - The UK’s F-35 stealt…

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 … Read more

Government Response

HM Treasury

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13 Recommendation Deferred

51st Report - The UK’s F-35 stealt…

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 … Read more

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 details of the government’s balance of investment across the full range of military capabilities, including the capability requirement identified by the Committee.

HM Treasury

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18 Recommendation Deferred

51st Report - The UK’s F-35 stealt…

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 … Read more

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 forward.

HM Treasury

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19 Conclusion Deferred

51st Report - The UK’s F-35 stealt…

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 … Read more

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 be brought forward.

HM Treasury

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20 Conclusion Deferred

51st Report - The UK’s F-35 stealt…

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 … Read more

Government Response

HM Treasury

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21 Recommendation Deferred

51st Report - The UK’s F-35 stealt…

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 … Read more

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

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22 Conclusion Deferred

51st Report - The UK’s F-35 stealt…

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 … Read more

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

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23 Conclusion Deferred

51st Report - The UK’s F-35 stealt…

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 … Read more

Government Response

HM Treasury

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24 Conclusion Deferred

51st Report - The UK’s F-35 stealt…

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 … Read more

Government Response

HM Treasury

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25 Conclusion Deferred

51st Report - The UK’s F-35 stealt…

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 … Read more

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

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Government Response AI assessment · 30 of 7 classified

Accepted 2

Acknowledged 6

Deferred 14

Rejected 8

Total 7 recs + 23 conclusions

Correspondence 4 letters

14 May 2026 To committee Letter from the Permanent Secretary at the Ministry of Defence relating to The UK’s Stealth Fighter Capability (recommendations 2a ,2b, 4 and 5a), 30 April 2026

Parliament page

20 Apr 2026 To committee Letter from the Permanent Secretary of the Ministry of Defence to the Chair of the Public Accounts Committee relating to The UK’s F-35 stealth fighter capability, 10 April 2026

Parliament page

26 Mar 2026 From committee Letter to the Permanent Secretary at the Ministry of Defence relating to Treasury Minute response – The UK’s F-35 stealth fighter capability

Parliament page

16 Oct 2025 To committee Letter from the Permanent Secretary of the Ministry of Defence relating to the oral evidence session on 08 September 2025 on the UK’s F-35 Stealth Fighter Capability, 25 September 2025

Parliament page