The UK purchase of F35As increases reliance on US systems – with limited benefits

The aircraft will add redundancy to NATO’s DCA mission but will not improve UK deterrence – and come at the cost of other urgently needed systems.

Expert comment Published 27 June 2025 4 minute READ

Dr Marion Messmer

Senior Research Fellow, International Security Programme

The UK government released a press statement shortly before the NATO Summit in The Hague this week, announcing the purchase of F35A fighter jets. The aircraft are intended to join NATO’s Dual Capable Aircraft (DCA) nuclear mission.

This move appears to have been intended both to enhance the UK contribution to NATO’s nuclear mission while also binding it even closer to the US.

The UK’s Strategic Defence Review (SDR), released weeks before, had recommended that the armed forces purchase F35As – to serve alongside the F35B (a short take off and vertical landing variant of the aircraft) currently flying with the Royal Air Force and Royal Navy. However, the SDR did not spell out how to arm the F35As. And the UK does not possess any nuclear weapons that could be deployed via the aircraft.

The F35As are certified to carry US B61-12 nuclear gravity bombs – low to intermediate yield nuclear weapons. And other states in NATO participate in the DCA mission do so by hosting these US nuclear weapons. With this purchase, it looks as if the UK is planning to do the same. But at what cost?

RAF nuclear storage sites

The F35As will be stationed at RAF Marham. That was the airbase where the UK’s own air launched nuclear weapons were based when it still had its own capability, decommissioned in 1998.

If the UK government wanted to host nuclear weapons there again, it would likely have to refurbish the storage site to be recertified for the purpose (if it has not already secretly been refurbished).

RAF Lakenheath, about 20 miles away, has already been undergoing a refurbishment process to become recertified as a nuclear storage site. This became known due to US Department of Defence budget documents that listed the UK as a US nuclear weapons storage site for the first time in 2022. 

The UK government has never officially commented on whether it was preparing to host US nuclear weapons again – US nuclear weapons had not been stored at Lakenheath since 2008 – but the refurbishment makes it seem highly likely that it is planning on hosting them there again.

Reasons for purchasing the F35A

The motivation for the move is clear: Russia has made a series of threats to use nuclear weapons in Ukraine. And, as tensions have risen, voices in the UK have argued for the restoration of a lower-yield nuclear weapon, to match Russian capabilities. This argument suggests that UK nuclear deterrence would be stronger if it could match Russian capabilities across an escalation ladder.

The thinking is that if the UK only has its Trident system available, Russia may risk using a low-yield nuclear weapon against the UK, in the belief that the UK would consider a response with Trident’s high yield strategic weapon an escalation too far.

Authorization for using US bombs would rest with the US president, rendering it a far from sovereign capability.  

But there is a compelling counter to this line of thinking: nuclear weapons tend to be seen as political rather than ‘useable’ weapons. 

Even the use of a low-yield nuclear weapon would represent a massive escalation that would bring unimaginable death and destruction, risking the spread of radiation far beyond its target area. In other words, any escalation to the nuclear level would carry massive consequences for the side that uses such a device.

Regardless of the theory behind the purchase, it would be very costly and time-consuming for the UK to redevelop its own air launch capability. 

Participating in NATO’s nuclear sharing arrangement is therefore seen by some as a halfway house: the UK does not have to develop its own tactical nuclear capability, but it will still get to participate in a lower-yield nuclear option. 

And it can demonstrate leadership within NATO by adding even more to its extended nuclear deterrence posture.

However, the main challenge with this approach is the question of launch authority for the weapons. Trident is a completely independent nuclear capability under the prime minister’s launch authority. But authorization for using US bombs would rest with the US president, rendering it a far from sovereign capability.  

One could argue that NATO’s nuclear sharing mission could be strengthened just by having additional UK aircraft and pilots available to train on their use and operate them in an emergency – and that there is therefore no need to host the weapons themselves on UK soil.

Effect on deterrence

But in either case, how much does this move truly add to NATO’s deterrence posture? The UK already contributes much more meaningfully to NATO’s nuclear deterrence through its existing Trident nuclear weapons system. 

The F35A purchase does add redundancy to NATO capabilities, which will undoubtedly add to the resilience of the deterrence posture. However, beyond that, the aircraft will be stationed much further West than other F35As in NATO, suggesting that they would not be the first to be used in a crisis.

Perhaps most notably, joining NATO’s nuclear sharing mission will further bind the UK to the US. Perhaps that is the intention – the UK has a long tradition of holding on tight when it seems that the ‘special relationship’ is on rocky footing. 

But it is not clear that this purchase will seriously affect US commitment to the UK or to European defence. It could be considered a signal that the US remains committed to extended nuclear deterrence in Europe. This is an important signal during an uncertain time. But this could still be undermined if the US withdraws conventional capabilities and troops from Europe.

There are a range of other, conventional systems, which would significantly strengthen the UK and NATO’s deterrence posture.

There are a range of other conventional systems which would significantly strengthen the UK and NATO’s deterrence posture – systems which are currently in short supply.

These include deep precision strike capabilities and additional air and missile defence capabilities – weapons which are far more likely to be used one day. And the UK could authorize their use independently. The SDR spells out plans to develop and procure such systems, but they seem to be much further down on the list of priorities than the F35s.   

Splitting the purchase between F35As and Bs could also mean that there will be fewer F35Bs available to constitute full air wings on the Royal Navy’s aircraft carriers, unless the UK intends to purchase more F35s overall over time.

The UK needs F35s for a range of missions. In that sense, purchasing a mix of F35As and Bs is not a huge departure from the original plans – but it ought not to be presented as a significant enhancement of the UK’s nuclear deterrence capability. The UK’s existing independent strategic nuclear capability is far more valuable in that regard.