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

The UK’s F-35 does not have a standoff weapon, and aircraft availability is inadequate. The Department states that its biggest concern with its F-35 fleet is the lack of a standoff weapon to strike ground targets from a safe distance. The Department wants to equip its F-35s with the Spear 3 missile but this is not likely to be in place until the early 2030s, partly because of problems with the supplier and partly because of global programme delays to the required software upgrades. The Department is attempting to bring forward Spear 3 delivery and integration and is considering other weapons for the interim as part of the Defence 2 Investment Plan. The Department acknowledges that, in addition to this limitation on capability, the F-35 fleet is not available as often as it should be, in large part because of personnel shortages and a lack of spare parts. recommendation a. The Department should set out in the Defence Investment Plan how it will ensure a standoff capability in the coming years before Spear 3 is fully integrated onto the aircraft b. The Department should write to the Committee, alongside its Treasury Minute response to this report, setting out how it intends to increase F-35 availability so that its targets are consistently met.

The F-35 programme faces an unacceptable shortage of several types of personnel, including engineers, cyber specialists, pilots and qualified flying instructors. The Department acknowledges that there are significant shortages of engineers in the F-35 programme, and that this is an impediment to operating the aircraft more often. This shortage reflects a shortage of engineers across the armed forces, which the Department is attempting to tackle with retention bonuses and increased capacity to train new recruits. However, the Department accepts that for F-35s this shortage had been exacerbated by its miscalculation of how many engineers are needed per aircraft. Even now that this mistake has been identified and funding provided for the 168 additional posts required, representing a 20% increase, it will take several years to resolve the shortage. The Department also acknowledges that there are significant shortages in other roles including cyber specialists, pilots and flying instructors. In 2025 only 5 out of 16 flying instructor posts were filled. recommendation The Department should produce a more radical plan to recruit and retain the highly skilled personnel necessary to work on and operate the F-35. The plan should include reference to accommodation as well as pay and other benefits that together provide an attractive offer over the long term.

Accommodation at RAF Marham is substandard, exacerbating issues with recruitment and retention. Despite the urgent need to address this, upgrades will not be completed under current plans until 2034. RAF Marham has been the main F-35 operating base since 2013, with at least 1,500 people working there on the F-35, many of whom also live in accommodation at the base. The Department accepts that accommodation at RAF Marham is not good enough and that these failings create a risk that people leave the service earlier than they otherwise would. The Department 3 has committed to removing all the worst grades of accommodation, which includes most of the accommodation at RAF Marham, from its sites. But it does not expect to complete this work at RAF Marham until 2034, albeit with some personnel expected to move into the first new block by the end of 2025. The Department claims that earlier investment was not possible because of the need for savings, and that upgrading accommodation at RAF Lossiemouth has been the higher priority. The 2034 date for relatively simple service accommodation construction is very complacent and should be given greater priority. recommendation The Department should urgently look to prioritise investment to bring forward completion of improvements to RAF Marham accommodation on a much earlier timescale than 2034. It should write to the Committee within 6 months as to how it intends to do this.

The Department has taken a narrow and short-term approach to management and costs and has failed to realistically appraise the programme’s whole-life cost. The Department acknowledges that it reduced the pace of aircraft deliveries to make short-term financial savings at multiple points in the programme, notably in 2010. In 2021 the Department decided to pause building a sovereign facility for assuring that aircraft retained their stealth capabilities, which is required for its freedom of action policy. The Department similarly delayed providing 809 Naval Air Squadron’s infrastructure by 6 years, increasing costs by almost £100 million. It did so despite knowing it would cost more money in the long-term and create a gap in capability. The Department also failed for many years to significantly update its public whole-life cost, which hardly increased from its 2013 estimate of £18.425 billion covering the first 48 aircraft to the then out of service date of 2048. In response to the 2025 National Audit Office report the MoD published a whole-life cost of almost £57 billion for all 138 aircraft to the new out of service date of 2069. But this still does not include non-equipment costs such as personnel, fuel and infrastructure which are included in the NAO estimate of £71 billion. recommendation The Department should: a. set out in its upcoming Defence Investment Plan the expected long-term impact on costs and capability of any short-term savings measures, on both the F-35 and other major programmes, and b. build on its recent whole-life cost analysis by including all relevant non-equipment costs to give a more complete through-life cost forecast of the programme. 4

The Department has not set out its preferred mix of F-35As and Bs, nor forecast the costs of introducing the F-35As in their nuclear weapons role. The 48 aircraft that the Department has contracted for so far are all F-35Bs, which can be flown from land or aircraft carriers. In June 2025 the Department announced that in its next phase of procurement it intended to buy 12 F-35As alongside 15 F-35Bs. The Department told us that the F35As would both act as training aircraft, where its additional range will be valuable in enabling longer training flights, and join the NATO dual capable aircraft nuclear mission. Only the F-35A variant can carry nuclear weapons. The Department acknowledged that becoming certified for the NATO nuclear mission will add new requirements to training, personnel and possibly infrastructure. The Department is speaking to other nations in the NATO mission about requirements for certification. This work is at an early stage and the Department did not provide any indication of forecast costs. recommendation The Department should update the committee in six months on what it expects the additional whole-life costs of operating Dual Capable Aircraft will be, and how long it will take to prepare the necessary arrangements. 5 1 F-35 capability requirements Introduction

On the basis of a report by the Comptroller and Auditor General, we took evidence from the Ministry of Defence (the Department) on its oversight and management of the UK’s F-35 fighter programme.1

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 delayed this to April 2025, then to December 2025, and introduced a more qualitative assessment of FOC. The Department expects to evidence FOC in part by deploying two full squadrons during the 2025 Carrier Strike Group (CSG) deployment. However, the National Audit Office’s report notes that “even if the MoD meets its FOC criteria, it will not yet have a force that can deploy sustainably.”11

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 8 Qq 87, 91; C&AG’s Report para 1.10 9 Q 118 10 C&AG’s Report, para 3 11 C&AG’s Report, paras 11, 1.19, 1.21 7 lenses: the state of the programme; the operational capability available; other defence lines of development including personnel, infrastructure, organisation and doctrine; and the contractual and legal situation.12 The Department told us that the decision to declare FOC is ultimately taken by the Chief of the Air Staff following a recommendation from the F-35 programme Senior Responsible Owner which is cleared through the chain of command.13

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 2030s. This is despite the Chief of the Defence Staff telling us that this was what worried him most about the F-35 and its capability.14 The Department also acknowledged that it will not have resolved personnel shortages that pose a risk to capability before the planned FOC declaration.15

The Department also told us that the 2025 CSG deployment, required for FOC declaration, had impacted availability before the deployment and would impact availability for some weeks after the deployment, because of the need for additional maintenance.16 The National Audit Office’s report noted that the impact of the deployment on operational readiness might last for several months.17 The flexibility of the training squadron was also impacted by the reduced number of aircraft available in the UK during the deployment.18 In order that FOC actually means what it says careful evaluation is needed in future to avoid premature unsubstantiated announcements. F-35 capability and availability

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 us that it had delayed building its sovereign Air Signature Assessment Facility (ASAF) to measure the stealth 12 Q 83 13 Q 81 14 Qq 88, 109 15 Q 104 16 Q 85 17 C&AG’s Report, para 1.21 18 Q 87 19 Qq 85, 104 20 Q 88 21 C&AG’s Report, para 1.11 8 characteristics of UK F-35 aircraft.22 Furthermore, aircraft availability is poor. The UK F-35 fleet achieved approximately one-third of the MoD target for the time it was able to fly all its required missions in 2024, and achieved only two-fifths of the level of availability of the global F-35B fleet between October 2024 and January 2025.23 The Department acknowledged that it was not getting the F-35 availability it wanted.24

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 has not yet been fully defined or timetabled and which the UK cannot directly influence.25 The Department acknowledged that delivery of Spear 3 is also negatively impacted by supplier performance.26 The Department also told us that it had delayed building the ASAF to save money for higher priorities elsewhere in Defence, acknowledging that this short-term saving would cost more money in the long-term.27

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 UK programme to include a UK weapon in its so-called digital accelerator which it hopes will speed up delivery. In the meantime, the Department told us that as part of its Defence Investment Plan it is considering buying other weapons that are already available and integrated.28 It also told us that it is working with Italy to measure the stealth characteristics of UK aircraft, although this arrangement only accounts for two aircraft per year.29

The Department also set out the reasons for poor availability of aircraft. It accepted that shortages of personnel, particularly engineers, impacted aircraft availability, and would continue to do so until they were resolved.30 Furthermore, the Department told us that the Global Support Solution, which supplies spare parts, is being reset by the United States so that it 22 Q 120 23 C&AG’s Report, paras 1.22-1.23 24 Qq 85, 104 25 Qq 109, 130 26 Qq 129-130 27 Qq 120-121 28 Q 109 29 Q 113; C&AG’s report, para 2.10 30 Q 104 9 can improve availability.31 The rates at which UK aircraft are unavailable because they are undergoing maintenance or waiting for spare parts are significantly higher than the target set by the global programme.32 31 Q 130 32 C&AG’s Report, para 1.27 10 2 F-35 personnel and accommodation Personnel

The F-35 programme suffers from personnel shortages across a range of occupations. A 2024 review of the programme, by the National Infrastructure and Service Transformation Authority (NISTA, formerly the Infrastructure and Projects Authority), stated that shortages of suitably qualified engineers represented the biggest threat to delivering F-35 capability. These shortages have been exacerbated by the Department miscalculating how many engineers were needed per aircraft because it failed to account for staff taking leave and performing other tasks including guard duties.33 The National Audit Office report also found that the programme is short of cyber specialists, pilots and qualified flying instructors. In 2025 the programme only had five full-time flying instructors compared to its target of 16.34

The Department acknowledged that the shortages across all these roles were very important, with the Chief of the Defence Staff stating that personnel had been one of his top two priorities in his previous role as Chief of the Air Staff. The Department told us that the training time required for engineers meant that it would take three or four years before the programme had the required numbers.35 This includes recruiting the 168 additional engineers—a 20% increase—required to address the shortage caused by miscalculating the number of engineers required per aircraft. The Department noted that the shortage of engineers is a problem that affects the whole of the armed forces.36

The Department told us that it has plans in place to fix its recruitment and retention problems. The Department also told us that it has increased its recruitment of engineers significantly in the last two years. It has offered joining bonuses for certain professions and has increased the capacity of its technical training skills to enable more recruits to be trained more quickly. 33 C&AG’s report, paras 2.3-2.4 34 C&AG’s report, paras 2.6-2.7 35 Q 101 36 Qq 101-102 11 To improve retention the Department offered a financial retention incentive for engineers, although this did not cover all supervisor grades where there have been especially acute shortages. The rate at which staff are leaving the armed forces, which was extremely high in 2022, has now stabilised at or below historic norms. However, the Department acknowledges that it takes time to adequately replace those experienced staff.37 Accommodation

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 the lowest-quality category of Ministry of Defence accommodation. Frontline personnel told the National Audit Office that accommodation was shabby and sometimes lacked hot water and that RAF Marham needed more amenities, such as bus access to a local town, to make it attractive to service personnel.39 This is completely unacceptable in today’s world. Servicemen and women on long tours of duty deserve decent accommodation for their families and themselves.

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 is working through investment choices as part of the Defence Investment Plan. The Chief of the Defence Staff told us that the Royal Air Force has committed to upgrading all its accommodation in the lowest two categories so that it meets the criteria for the highest two categories. Across the whole Royal Air Force estate this will cost more than £1.5 billion over approximately 15 years.40

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 takes to train specialist staff such as engineers.42 37 Q 101 38 C&AG’s report, para 3.27 39 C&AG’s report, para 2.13 40 Q 105 41 Q 107 42 Qq 101, 103 12 The Department also told us that it needs to upgrade accommodation so that staff become more engaged and feel more valued, with the implication that poor accommodation reduces personnel engagement.43

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 will not be completed until 2034. The Department acknowledged that it would have preferred to have upgraded the accommodation earlier to coincide with personnel arriving to work on F-35. But it said that this was not possible because it needed to make savings and prioritised preserving its operational output over upgrading infrastructure.44 We believe this length of time for refurbishment is unacceptable and have asked the Department to write to us to say how this can be accelerated. The Department told us that it had made significant investment in upgrading single-living accommodation at RAF Lossiemouth, which was a few years ahead of RAF Marham in the programme, and linked that to the workforce there feeling engaged, valued and invested in.45 43 Q 107 44 Q 105 45 Q 107 13 3 F-35 costs and future procurement 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 in the short-term out to 2024–25, it will have cost the Department £16 million more than that by 2031–32 because of inflation resulting from choosing to build later. The Department viewed this as a “conventional consequence” of managing an annual departmental budget covering many programmes.47

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. But to save money the Department decided to delay the delivery of the infrastructure to 2029. As a result of raw material and workforce cost increases, the Department now forecasts that the construction will cost £154 million despite a reduction in requirements.48

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 The ASAF will not now be delivered until 2032.50 Since its formation in 2023, 809 Naval Air Squadron has been using 617 Squadron infrastructure along with recently-provided temporary accommodation until its permanent infrastructure is delivered.51 46 Q 124 47 Qq 120-122 48 Letter from MoD to PAC, 25 September 2025 49 C&AG’s Report, paras 1.11, 2.9-2.10 50 Letter from MoD to PAC, 25 September 2025 51 C&AG’s Report, para 2.12 14

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 financial reasons.54 It is unclear whether the 2010 delay has caused increased costs since the increase in costs resulting from inflation may have been offset by a decreased unit cost of the aircraft over time.55 In correspondence provided after our evidence session, the Department stated that, in its view, the effect of delay was marginal if not cost neutral.56

In 2013 the Department set out a whole-life cost for the F-35 programme of £18.4 billion, although this only covered the first 48 aircraft out of the 138 that the UK has announced it intends to buy. Before the publication of the National Audit Office report in 2025 this figure had only increased to £18.76 billion and had not taken account of the changed out-of-service date from 2048 to 2069.57 The Department has since published a whole-life cost for 138 aircraft out to 2069 of £57 billion. In correspondence provided after our evidence session the Department stated that this figure was based on the A variant for the final 63 aircraft, which is cheaper than the B variant, and that it does not include related costs such as personnel, infrastructure and fuel.58 The National Audit Office calculated that if these related costs were included the whole-life cost would be £71 billion.59

The Department told us that its approach to whole-life costs gave it the right cost information for the management decisions it needs to make. It argued that coming up with a whole life cost out to 2069 was not helpful for budgeting because the Defence budget deals with much shorter timeframes and planning assumptions such as the variant mix of future purchases are yet to be firmly decided upon. The Department acknowledged that the whole-life cost it has ultimately come up with does not include all costs associated with the F-35. It argued that this was reasonable, claiming that some costs, such as fuel, would be incurred regardless of the F-35 programme. We believe that the Department’s approach does not best support sound financial management over the long term. 52 Qq 68-69 53 Q 79 54 C&AG’s Report, para 3.15 55 Qq 69-70, 77 56 Letter from MoD to PAC, 25 September 2025 57 C&AG’s Report, para 3.29 58 Letter from MoD to PAC, 25 September 2025 59 Q 97; C&AG’s Report, para 3.34 15 Future procurement

The Department is deciding what mix of the two F-35 variants to buy in its procurement process. In Phase 1 the UK has contracted for 48 F-35Bs, which can fly from land bases and aircraft carriers. In June 2025 the Department announced its intention to buy 12 F35As, which cannot fly from aircraft carriers, but which can carry nuclear weapons, as part of its next phase of 27 aircraft.60 The Department told us that it has not yet decided which variants to buy beyond the next procurement phase.61 That decision will be considered in future defence strategic reviews and investment plans.62

The Department told us why it had decided to purchase some A variants. The A variant can fly further for longer than the B variant, because it does not have the weight limitations that come with the ability of the B variant to do short take-off and landing on aircraft carriers and can carry extra fuel. The Department told us that the A variants will be routinely used on the training squadron, meaning that more training can be completed on each sortie and therefore pilots can be trained more quickly. The Department also noted that the dual nuclear weapons capability of the A variant will enable the UK to contribute to the NATO nuclear mission.63 The Department also told us that the A variant is 20% to 25% cheaper than the B variant, and slightly cheaper to support.64

The Department explained that it is starting to understand the practical requirements of becoming certified for the NATO nuclear mission. The Department needs to meet standards for handling, loading and using nuclear weapons. These standards are set by the United States since it provides the weapons, and the Department is learning from other nations that have been, or are becoming, certified. The Department told us that certification covers ground crew, pilots, infrastructure and the aircraft itself. It expects that there will be a requirement for additional training and potentially for additional personnel as well, although it does not expect to need significant additional infrastructure.65 We believe it is a reasonable assumption that this may end up proving more expensive. 60 C&AG’s Report, paras 2, 6 61 Q 117 62 Q 91 63 Q 92 64 Q 97 65 Q 96 16