F-35 Lightning II: The Fighter That Keeps Getting More Powerful, More Important and More Expensive
The world’s most ambitious fighter programme enters another crucial phase
The F-35 Lightning II has never been simply another combat aircraft. Conceived as a stealth fighter that could be produced in different versions for conventional airfields, aircraft carriers and short take-off operations, it has developed into one of the central pillars of Western air power. Almost 1,300 aircraft were in the global fleet by the beginning of 2026, according to manufacturer Lockheed Martin, and the programme now stretches across the armed forces and defence industries of the United States and numerous allied nations. Yet the extraordinary technological ambition of the F-35 continues to be accompanied by another familiar feature: cost, delay and an increasingly complicated struggle to keep a rapidly growing fleet operational.
When Cicero’s first examined rising F-35 costs in 2023, attention centred on production Lots 15 to 17, inflation, the introduction of Technology Refresh 3 and the long-awaited Block 4 modernisation programme. Three years later, the aircraft remains in expanding production and demand from allied countries remains considerable. The technological upgrade programme, however, has proved far more difficult than originally envisaged, while independent US government scrutiny continues to raise serious questions about readiness, sustainment costs and the timetable for delivering the fighter’s promised capabilities.
Production accelerates after years of disruption
Lockheed Martin says it delivered a record 191 F-35s during 2025, substantially exceeding its previous annual delivery record of 142 aircraft. The company says the worldwide fleet has now accumulated more than one million flight hours. The F-35 programme has therefore moved far beyond its earlier status as an expensive developmental project and become an enormous operational system involving aircraft, engines, software, maintenance facilities, training establishments and supply chains spread across numerous countries.
The next production stage is equally substantial. Lockheed Martin and the F-35 Joint Program Office reached agreement covering production Lots 18 and 19 for up to 296 aircraft, under contracts valued at approximately $24 billion. Those numbers demonstrate the unusual scale of the programme. Despite decades of controversy over its cost and development, governments are not abandoning the F-35. In several cases they are increasing their commitments to it.
That commercial and military success does not mean the programme’s underlying problems have disappeared. Indeed, the sheer size of the F-35 fleet means that problems involving software, engines, spare parts or maintenance can have consequences extending across the air forces of numerous countries.
Block 4 remains the technological prize and the problem
At the centre of the current programme is Block 4, the collection of hardware and software improvements intended to give the F-35 greater processing power, improved electronic warfare capabilities, new weapons integration and enhanced sensing and communications. Much of that capability depends upon Technology Refresh 3, usually known as TR-3, which introduces substantially improved computing hardware to the aircraft.
The US Government Accountability Office reported in September 2025 that Block 4 was already more than $6 billion above its original estimate and at least five years behind its original completion timetable. The Pentagon has consequently been restructuring the programme and reducing or reorganising elements of its scope in an attempt to deliver capabilities at a more predictable pace.
TR-3 itself became one of the principal causes of delayed aircraft deliveries. According to the GAO, Lockheed Martin delivered 110 F-35s during 2024 and every one was late, with the aircraft arriving an average of 238 days behind schedule. That compared with an average delay of 61 days during 2023. The GAO identified TR-3 as the primary cause of those delays.
The picture improved substantially during 2025, when Lockheed reported its record delivery year and said the most advanced TR-3 software had been delivered. Nevertheless, the transition remains unfinished for some existing aircraft. In Britain, the Ministry of Defence told Parliament in June 2026 that the timetable for upgrading the remaining UK F-35B fleet to the TR-3 standard had yet to be finalised.
Britain completes its first F-35B fleet
For the United Kingdom, 2026 has marked an important milestone. In May, the final two aircraft from Britain’s initial F-35B procurement arrived at RAF Marham. The Royal Air Force said their arrival brought the operational UK fleet to 47 F-35Bs and completed the initial procurement phase.
The British F-35B force is jointly operated by the Royal Air Force and Royal Navy. The aircraft can operate from RAF Marham as well as from the Queen Elizabeth-class aircraft carriers, giving Britain a fifth-generation combat aircraft capable of operating from land or sea. The Lightning Force includes 617 Squadron, the famous Dambusters, 809 Naval Air Squadron and 207 Squadron, which provides operational conversion and training.
The F-35B’s short take-off and vertical landing capability makes it particularly important to Britain’s carrier strategy. Unlike the conventional F-35A, it can operate from the ski-jump decks of HMS Queen Elizabeth and HMS Prince of Wales without the catapults and arrestor equipment used aboard conventional American aircraft carriers.
Britain turns to the F-35A
Britain’s relationship with the F-35 is now entering a new and politically significant phase. In June 2025 the Government announced that the UK would purchase at least 12 F-35A aircraft as part of its next procurement package. Unlike the F-35B, the F-35A is designed primarily for conventional runway operations and cannot operate from Britain’s aircraft carriers.
The Government argues that the F-35A offers financial as well as operational advantages. It estimated that purchasing 12 F-35As rather than another 12 F-35Bs could save as much as 25 per cent per aircraft. The aircraft are intended to be based at RAF Marham and will also be used by the Operational Conversion Unit, potentially allowing the more expensive and specialised F-35Bs to concentrate on frontline and carrier operations.
The decision also has a much wider strategic significance. Britain intends to use the F-35A to rejoin NATO’s dual-capable aircraft nuclear mission, restoring a nuclear role to the Royal Air Force for the first time since Britain’s sovereign air-launched nuclear weapons were withdrawn after the Cold War. The nuclear weapons associated with NATO’s dual-capable aircraft mission remain American weapons under US custody and control.
The Government’s Defence Nuclear Enterprise update, published in September 2026, confirmed that preparations for Britain’s participation are progressing and that the UK will join the NATO mission once its F-35A aircraft have been delivered. Discussions with the F-35 Joint Program Office over the procurement profile and delivery schedule were still continuing in September, with ministers saying that the next British batch is planned to contain at least 12 F-35As.
The three versions of the F-35
The F-35 programme continues to revolve around three closely related but significantly different aircraft. The F-35A is the conventional take-off and landing version and is the lightest and most widely used variant. The F-35B sacrifices some range and internal capacity in return for its short take-off and vertical landing capability, allowing it to operate from smaller carriers and austere locations. The F-35C has larger wings and structural changes designed for catapult launches and arrested landings aboard large US aircraft carriers.
That common design was originally intended to deliver economies of scale while providing different services with aircraft suited to their individual requirements. In practice, maintaining three variants while continuously modernising their sensors, computers, engines, weapons and software has contributed to the extraordinary complexity of the programme.
The cost has moved far beyond the price of the aircraft
Discussion of the F-35 frequently concentrates on the purchase price of an individual fighter, but that figure tells only part of the story. The much larger financial challenge lies in maintaining, upgrading and operating thousands of aircraft for decades.
The GAO estimates that Block 4 modernisation, engine and power and thermal-management improvements, and the cost of maintaining and operating the planned US fleet of 2,470 aircraft over its 77-year lifecycle will exceed $2 trillion. That figure should not be confused with the purchase price of the aircraft themselves. It represents the extraordinary lifetime scale of America’s commitment to the programme.
The Pentagon is attempting to address some of those pressures. In 2025 it launched what it calls the Global Support Solution Reset, a new strategy intended to improve F-35 readiness by 2030. According to the GAO, however, the strategy itself requires an estimated $13.7 billion more than previously planned through the 2031 financial year.
The difficulties include shortages of spare parts, dependence upon contractors and limitations in industry’s capacity to supply the enormous global fleet. These are no longer merely development problems. They are the logistical consequences of operating one of the largest and most technologically complex combat-aircraft programmes in history.
Readiness remains the uncomfortable statistic
Perhaps the most troubling recent figures concern aircraft availability. In June 2026 the GAO reported that the F-35 fleet’s mission-capable rate, meaning the proportion of time aircraft were capable of performing at least one of their assigned missions, had fallen from 67 per cent in fiscal year 2021 to 44 per cent in fiscal year 2025.
The full mission-capable rate, measuring aircraft capable of performing all of their assigned missions, declined from 38 per cent to 25 per cent over the same period. Those figures sit uncomfortably beside the programme’s technological achievements and rapidly expanding international footprint.
The Pentagon and industry are attempting to improve that performance, but the GAO has warned that shortages of components and industrial capacity could frustrate the new readiness strategy. It also found that hundreds of millions of dollars in contractor incentives paid since 2020 had not produced the intended improvements in readiness.
The engine must grow with the aircraft
Modernisation also places increasing demands on the Pratt & Whitney F135 engine. More powerful computers, sensors and electronic systems require greater electrical generation and cooling capacity, creating a problem that cannot simply be solved through software.
Pratt & Whitney announced on 15 September 2026 that its F135 Engine Core Upgrade had completed a significant risk-reduction design review. The company says the upgrade is intended to provide the additional power and thermal-management capacity required by Block 4 and future capabilities while preserving engine life.
This less glamorous aspect of the programme may prove critical. A fighter can carry increasingly sophisticated radar, electronic warfare equipment and computing systems only if its engine and thermal-management architecture can provide sufficient power and dispose of the heat those systems generate.
An aircraft too important to judge by one number
The F-35 therefore presents an unusual contradiction. It has suffered enormous development delays, modernisation problems, rising lifetime costs and persistent difficulties keeping enough aircraft ready for operations. Those criticisms are not simply the arguments of the programme’s opponents; many come from the US Government’s own independent auditors.
At the same time, the programme continues to expand. Aircraft are being delivered in greater numbers, allied nations continue to buy them, and the F-35 has become deeply embedded within NATO air power. Britain has completed its initial F-35B procurement and is preparing to introduce a second variant, while manufacturers and governments continue investing in the technologies intended to keep the aircraft relevant for decades.
The debate surrounding the F-35 has consequently matured. The question is no longer simply whether the aircraft was too expensive to develop. Hundreds of aircraft are already operational and an international military and industrial infrastructure has grown around them. The more pressing question is whether governments can afford to operate, maintain and continuously modernise that fleet at the scale now envisaged.
From controversial project to permanent military infrastructure
When the F-35 was conceived, its advocates promised that one basic aircraft family could replace numerous ageing fighter types while giving allied forces stealth, advanced sensors and unprecedented information-sharing capabilities. The resulting programme became vastly more complicated, expensive and politically contentious than those early ambitions suggested.
Yet the F-35 has also survived virtually every controversy surrounding it. Production continues, the international fleet continues to grow, and its role within Western defence planning is becoming deeper rather than smaller. Britain’s decision to add the F-35A to its existing F-35B force, including a future NATO nuclear role, demonstrates how strategically embedded the aircraft has become.
The F-35 Lightning II of 2026 is therefore neither the straightforward success story promoted by its manufacturer nor simply the expensive failure portrayed by some of its critics. It is something considerably more consequential: a hugely capable but extraordinarily complex weapons system whose strengths, costs and shortcomings will shape Western air power for decades.
For Britain, the next chapter is already beginning at RAF Marham. For the wider F-35 programme, however, the challenge remains the one that has followed the aircraft throughout its history: turning extraordinary technological ambition into an affordable, available and dependable fighting force.
The United States is proposing to sell Saudi Arabia American-built F-35s.
And the timing is striking because this has moved forward just in the past week. On 17 September 2026, the US State Department approved a possible $24.3 billion sale of 48 F-35 Lightning IIs to Saudi Arabia, together with 49 Pratt & Whitney F135 engines, support equipment, software, training and logistics. The deal still requires the US congressional process, so the Saudis haven’t simply taken delivery of 48 aircraft.
President Trump had publicly said in November 2025 that his administration intended to sell F-35s to Saudi Arabia, and the White House subsequently described future F-35 deliveries as part of the expanding US-Saudi defence relationship.
There’s a very interesting angle for your updated F-35 article, because Saudi Arabia would become the first Arab state to operate the aircraft if the transaction is completed. Israel is currently the only Middle Eastern country operating F-35s, so the proposed sale also raises the longstanding US requirement to preserve Israel’s qualitative military edge.
