• 37 F-35 stealth fighter aircraft currently in service, against a commitment to eventually purchase 138 aircraft. The F-35 is technologically far superior to any previous UK military aircraft. 
  • Aircraft availability, pilot flying hours and overall UK F-35 capability are currently lower than expected due to MoD and global programme failings.
  • £18.76 billion whole-life cost forecast by MoD is considerably lower than the NAO’s £71 billion estimate, which factors in aircraft, personnel and infrastructure costs.

The combined shortcomings of the global and UK F-35 stealth fighter aircraft programme – including delays, lower-than-expected availability, infrastructure gaps and personnel shortages – are undermining the armed forces’ warfighting capability, although some significant military and economic benefits have been achieved, according to a new National Audit Office (NAO) report.1

The Ministry of Defence (MoD) began taking delivery of F-35B aircraft in 2012,2 as part of a global programme run by the Joint Program Office (JPO) in Washington, D.C. It has committed to purchasing 138 aircraft, with 38 having been received another 10 on order but no approved timetable for purchasing the rest.3 The MoD expects its F-35 aircraft to remain in service until 2069.

The F-35 is significantly superior to any previous UK aircraft, particularly in its stealth capabilities, its fusion of information from different sensors and its electronic warfare technology.

But the UK programme is experiencing delays. Plans to equip the aircraft with important weapons, including the integration of UK-developed missiles, and to assure the MoD that the aircraft retains its stealth capabilities have been pushed back until the 2030s.4 Full delivery of the first batch of 48 aircraft is also behind schedule due to a combination of financial pressure and problems with the global programme.5 This means that the MoD now expects to declare Full Operating Capability at the end of 2025, two years later than planned, and with several gaps against its initial requirements.

Other ongoing issues facing the UK programme include personnel shortages across a range of roles, most significantly in engineering posts; difficulty in securing spare parts and support equipment from the global programme; and poor aircraft availability rates, resulting in fewer flying hours for pilots than the MoD wants.6

The MoD has spent £11 billion to date on its F-35 programme – more than it has reported, and more than it anticipated it would spend at the time of the 2013 business case.7 The NAO has also estimated the whole-life cost of the programme to the UK to be £71 billion – considerably higher than the £18.76 billion the MoD has publicly reported.8

Committing early to the global programme has helped bring the UK industrial and other benefits. For instance, UK companies now manufacture at least 15% by value of all F-35 aircraft, even though the MoD is buying under 5% of total production. This has so far resulted in £22 billion of contracts for UK companies.

Day-to-day programme management has benefitted from strong leadership and robust processes, but some longstanding MoD practices act as barriers to more effective management and increased capability. To overcome these barriers, the NAO recommends that the MoD considers structural changes, such as extending the length of senior programme staff tenures, providing appropriate financial and commercial freedoms, simplifying lines of accountability, and streamlining approvals regimes.

To provide a more robust basis for future investment decisions, the NAO further recommends that the MoD develops, maintains and updates a whole-life assessment of the value it intends to deliver through its F-35 programme. This should include a clear weighting of all military and non-military benefits, including a tighter measurement of the capability of the F-35 aircraft based on high-level characteristics and key user requirements. It should also fully calculate future forecast costs, building on its new whole-life cost calculation.

“The F-35 programme offers significantly improved capability and considerable economic benefits to the UK. But the capability benefits are not being fully realised due to delays, infrastructure gaps and personnel shortages.

“The MoD now needs to decide where to prioritise its resources to improve capability in a way that maximises the full benefits of the F‑35 programme to the UK.”

Gareth Davies, head of the NAO

Read the full report

The UK’s F-35 capability

Notes for editors

  1. The report will be available on the NAO website via the following link from 00:01 Friday 11 July: https://www.nao.org.uk/reports/the-uks-f-35-capability/ 
  2. The F-35B aircraft is a variant that can be used from land or aircraft carriers. See Figure 1 of the report for the attributes of the F-35’s A, B and C variants.
  3. The UK has received 38 aircraft but currently only has 37 in service because one was lost in an accident in November 2021.
  4. Despite these gaps, the MoD believes it can declare that the aircraft has Full Operating Capability by the end of 2025, although this is two years later than what was set out in the 2018 Concept of Use.
  5. In 2010, the MoD removed £1.5 billion from the F-35 budget, and since then Air Command has delayed delivery of F-35 aircraft on several occasions, most recently in 2020 when it delayed a batch of seven aircraft by a year to 2025 to save money. More widely, the global programme has suffered from manufacturing problems with both aircraft and engines, and recent issues have meant that the completion of Block 4 upgrades is also running late. In 2023, the global programme delivered 91% of aircraft and 100% of engines late.
  6. In 2024, the UK F-35 fleet had a mission capable rate (defined as the ability of an aircraft to perform at least one of its seven possible required missions) that was approximately half the MoD’s target. It had a full mission capable rate (defined as the ability of an F-35 aircraft to perform all its required missions) that was approximately one-third the MoD’s target. The MoD’s targets are themselves lower than global programme targets. The NAO is not disclosing actual percentages for national security reasons. The poor availability rates are driven largely by a UK shortage of F-35 engineers and a global shortage of F-35 spare parts. Problems with aircraft availability have resulted in pilots receiving fewer flying hours than the MoD wants. Even after the MoD reduced the flying requirement from 10 hours per month to approximately 7.5 hours per month the number of flying hours was insufficient to meet this requirement for all pilots in post as of March 2024.
  7. The MoD monitors only the amount it spends on equipment and support, on which it reports spending £9.35 billion on the F-35 programme by the end of March 2025. If spending on personnel, infrastructure, training flights, other overheads and earlier sunk costs are included, the NAO estimates this would add at least £1.5 billion to the total. The 2013 business case stated that the F-35 would be comparable to, or cheaper than, fourth-generation fighters such as Typhoon. But higher-than-forecast global programme production, development and support costs since then are proving this to be over-optimistic.
  8. The MoD’s public forecast of £18.76 billion assumes only 48 aircraft will be procured and that their out-of-service date will be 2048, even though MoD policy is to procure 138 aircraft and take them out of service in 2069. Following NAO prompting, the MoD has forecast that the cost of 138 aircraft to an out-of-service date of 2069 would be just under £57 billion, although it describes this forecast as pessimistic and notes that it has not been subject to independent validation. This figure does not include non-equipment costs, such as personnel, fuel, and much infrastructure. The NAO estimates that these costs would add £14 billion to the MoD’s forecast, resulting in a full whole-life cost of £71 billion.

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