The United Kingdom was the sole Tier 1 partner in the F-35 programme, committing to the eventual purchase of 138 aircraft and contributing about 10% of the planned development costs. The UK’s overall procurement target of 138 F-35s was set in 2006, which at the time represented the largest agreed total among the programme partners behind the US Air Force, US Navy and US Marine Corps.

The UK Ministry of Defence’s (MoD’s) commitment to 138 F-35 Lightning aircraft gave the UK a prominent position in the global programme and helped to win UK companies (often through US subsidiaries) a significant share of production. This has been claimed to be equivalent to 15% of the value of each F-35 produced. It is worth noting that the 138-aircraft total represented cumulative purchases spread over several decades and not a simultaneous operational fleet of anything like that size.

This large total ‘commitment’ also imposed costs on the UK. The F-35 Joint Program Office (JPO) uses a so-called Composite Share Ratio (CSR) to calculate ‘non-recurring’ costs including capability development and for work on integrating nation-bespoke capability, such as weapons, onto the aircraft.

The CSR is calculated according to the number of aircraft partner nations are committed to purchase as a percentage of the total (the UK CSR is based on a commitment for 138 aircraft and a global total of 3,088 aircraft ordered/committed to up to 2019). The suspension of Turkey from the F-35 programme in 2019 increased the UK contribution from 4.47% to 4.62%.

A non-binding commitment

The UK ‘commitment’ did not, in fact, commit the MoD to any further purchases beyond the 48 F-35B short take-off/vertical landing (STOVL) aircraft already contracted for and the UK has not approved any additional procurement since 2016. This means that the UK has contracted for a lower percentage of its publicly committed number of aircraft compared to most other partners, with the MoD noting that this (let alone any future reduction in the planned programme) could put UK industry contracts at risk.

From the very beginning of the programme there were doubts as to whether the UK commitment to 138 aircraft would ever be exercised, although that total was confirmed as an ‘aspiration’ in the 2015 Strategic Defence and Security Review. It has been reported that just 66 serial numbers were allocated, reflecting the actual UK requirement, which has been variously estimated at 64-75 aircraft in order to support the UK’s carrier strike capabilities through to the planned 2069 out-of-service date (OSD) of the Royal Navy’s (RN’s) Queen Elizabeth-class aircraft carriers, including training aircraft and attrition. The F-35’s OSD was also given as 2069. There was no plan to be able to deploy two carrier air wings simultaneously and it was assumed that any extra aircraft would be to meet Royal Air Force (RAF) requirements for land-based operations.

The 2021 Integrated Review failed to increase UK F-35 orders and the government moved away from explicitly confirming the 138-aircraft total in its 2021 Defence Command Paper, instead stating only that the fleet would grow beyond the 48 aircraft then on order.

On 23 March 2021, while welcoming the Integrated Review, the First Sea Lord, Admiral Tony Radakin, reportedly estimated that the final fleet would total between 60 and 80 aircraft.

Ministers verbally restated the 138 lifetime total fleet goal in February 2024 but demurred from giving firm timetables or contracts for the remaining aircraft, although it was clear that the second tranche would be smaller than the notional 90 aircraft remaining from the UK commitment. In an 8 March 2024 letter to Jeremy Quin MP, the chair of the House of Commons Defence Committee, James Cartlidge MP, then the Minister of State for Defence Procurement, wrote that “negotiations regarding the ‘Tranche 2’ buy of a further 27 F-35 aircraft are going well.” This would “bring the UK fleet up to 74 aircraft” and “realise our long-term ambition to deepen Carrier Enabled Power Projection capability”.

F-35As for the RAF

The National Audit Office (NAO) issued a report on ‘The UK’s F-35 capability’ in July 2024 and this maintained the fiction that the UK would, eventually, order 138 aircraft. At much the same time anonymous sources began to suggest that the ‘second tranche’ of F-35s might include a mix of F-35B and conventional take-off F-35A variants and that Air Commodore Jim Beck, then the Assistant Chief of Staff (ACOS) Capability Strategy at Headquarters Air Command, had put in a business case for seven F-35As for Operational Conversion Unit (OCU) training. This business case was made on the basis that the F-35As had a lower unit price and lower operating costs, could fly longer sorties and would ‘free up’ B models then used by No 207 Squadron: the Lightning OCU. The idea was seen by many as being a ‘Trojan Horse’ for those in the RAF who favoured acquiring larger numbers of F-35As to meet RAF requirements for a land-based strike/attack aircraft.

UK F-35s and the DCA mission

By the time the incoming Labour government published its Strategic Defence Review on 2 June 2025 the number of F-35As had grown to 12 aircraft (of a second tranche total of 27 F-35s) and their role had apparently expanded.

On 24 June 2025 Downing Street announced that the UK would “purchase 12 new F-35A fighter jets and join NATO’s dual capable aircraft [DCA] nuclear mission”.

The then prime minister, Sir Keir Starmer, explained the strategic rationale for the F-35A procurement, noting that “the UK is confronting a new era of threat, including rising nuclear risks”. There has long been a perceived need to address the significant imbalance in non-strategic nuclear capabilities between NATO and Russia, which risks Moscow gaining ‘escalation dominance’ in any future crisis or conflict.

In September 2025 the Chief of the Air Staff, Air Chief Marshal Sir Harv Smyth, stated, “A nuclear-capable Lightning presents the UK with a mechanism to provide considerable support to our ‘NATO First’ approach and NATO’s nuclear mission” and that it would “offer NATO additional robust, credible and capable response options”.

That was true, but ACM Smyth’s additional claim that it added an “important rung to our escalation ladder: one that has been missing from the UK’s political, diplomatic, and military toolset for nearly three decades”, was much more debateable. The DCA arrangement essentially provides a new rung on a US-owned, US-controlled escalation ladder, not a British one. ACM Smyth said that he would “expect potential adversaries to take note of this change”, but sceptics could see no real change to the UK’s fundamental position.

This is because the NATO DCA mission (also referred to as NATO nuclear sharing) is based on the carriage of US-supplied, US-controlled, low-yield B61 nuclear freefall bombs by some NATO partner air forces. Until recently the B61 was carried by German and Italian Tornados and by Belgian, Dutch and Turkish F-16s, although Belgium, Italy and the Netherlands are transferring (or have transferred) the DCA role to the F-35A.

The otherwise non-nuclear NATO allies involved provide aircraft, aircrew and infrastructure, while the US provides the nuclear gravity bombs. Although these allies share operational planning through the NATO Nuclear Planning Group, the United States maintains custody, absolute control and final authorisation authority over the forward-deployed nuclear weapons at all times.

The reliance on US permissions and authorisation means that the DCA mission in no way represents an independent or sovereign capability. Indeed, it is increasingly seen as representing a potential vulnerability, given shifting US attitudes to its European NATO partners.

Once operational in the DCA role, the UK’s F-35As will be capable of delivering B61-12 nuclear free-fall bombs (if and when released from US custody). Supporters claim that the RAF F-35As will thus boost the UK’s deterrence contribution to NATO during a time of growing nuclear threat in Europe. Cynics, meanwhile, suggest the RAF will become “an Uber driver delivering American nukes at America’s direction” and question how ‘deterred’ Russian President Vladimir Putin might be by weapons whose use is ultimately controlled by US President Donald Trump.

Even before Trump, there were some doubts about the US nuclear guarantee in Europe, not least because US territorial integrity was only at risk if a European conflict escalated to the strategic level, giving the US a powerful incentive to limit the power to escalate a conflict to itself, and out of the hands of European nations whose territory might actually be at risk.

As recently as 20 July 2026 Luke Pollard MP, UK Minister of State for Defence Readiness and Industry, repeated that the 12 F-35As being acquired will “allow the UK to join NATO’s Dual Capable Aircraft (DCA) mission”.

This directly contradicted Air Vice Marshal Jim Beck, now the RAF’s Director Capability and Programmes. AVM Beck had said at the Global Air & Space Chiefs’ Conference in London on 16 July 2026 that the 12 F-35As to be ordered by the UK were not being purchased to perform the NATO dual-capable aircraft mission. “For any clarification, or to avoid any doubt, we did not buy those 12 aircraft for dual-capable aircraft capability,” he said. “We bought them for our conversion units. At the same time, we stated we would get back into the dual-capable aircraft role supporting NATO. The two are separate.

“We’re doing the analysis to understand the size and posture of force that we will need,” said AVM Beck, emphasising that the training and DCA functions were entirely separate undertakings that should not be conflated and implying a need for further F-35A procurement for the new nuclear role.

But when will we get them?

In answer to questions by Stuart Anderson MP, James McCleary MP and Baroness Goldie, Pollard wrote, “The exact delivery profile and date of F-35 aircraft is subject to negotiation between the UK and multinational Joint Program Office, but the UK anticipates taking delivery of the next batch of F-35 aircraft from the early 2030s.”

This answer confirmed that no new ‘Tranche 2’ F-35s will be delivered before 2030, failed to confirm the planned 27-aircraft total and failed to guarantee that the new batch would include any F-35B models.

In answer to a subsequent question from Ben Obese-Jecty MP, Pollard confirmed that all 13 F-35 aircraft produced for the UK in Lots 15-17 had been delivered and that no aircraft are scheduled to be produced for the UK in Lots 18-22. Lot 22 will be built to meet US Fiscal Year 2028 orders, for delivery in/from 2030.

This means that the UK will not receive any additional aircraft beyond the 47 now in service for at least four years, while the combat air fleet will remain at its present pitiful level. Some are concerned about the impact on UK carrier strike capabilities, although the RN’s plans for so-called hybrid air wings mean that in future carriers will embark a smaller number of manned F-35Bs alongside new unmanned platforms.

Project Vanquish, a joint RN/RAF programme, will see flight trials of a high-subsonic, jet-powered uncrewed autonomous collaborative platform from one of the RN’s Queen Elizabeth-class carriers during 2026. The aircraft is supposed to be capable of short take-off and landing without recourse to catapults or arrestor gear. This experiment is supposed to inform development of the RN’s hybrid air wing concept as part of the Maritime Aviation Transformation (MATX) programme. What follows is intended to see a transition to a largely uncrewed Fleet Air Arm by 2040, so it may be that the F-35B’s time as part of any hybrid air wing will be brief in any case.

Others are more sanguine about the pause in F-35 orders, reasoning that no sane person would order the type until the present issues with its Technology Refresh 3 (TR-3) and Block 4 upgrades have been solved and until there is greater confidence in the rapid integration of UK weapons and a more rapid iteration cycle for mission data, including sovereign mission data files.

Some believe that the UK should bring its F-35 procurement to a close now. With the new Tempest sixth-generation fighter being developed under the Global Combat Air Programme due to enter service in 2035 (and with strong pressure to bring forward that in-service date date by up to two years), the simultaneous acquisition of increasingly obsolescent F-35As would appear questionable at best, representing a diversion of scarce budgetary resources and of attention and effort away from the vital GCAP project.