In 2025, Lockheed Martin’s F-35 Lightning II program achieved a milestone that once seemed unlikely: a record-breaking year of deliveries. With nearly 200 aircraft handed over to air forces across the globe in just one year, the program appeared to have turned a corner after years of delays, certification issues, criticism, ever-increasing costs, and political scrutiny. But behind the impressive production figures, there is a more complicated operational reality, one that continues to trouble the military forces and auditors. In our article, we will explore why the F-35 can be both the world’s most popular fifth-generation fighter and one of its most persistently challenged.

The F-35 is a unique fighter jet in many ways. First, it was designed to replace a variety of older aircraft, from traditional designs like the F-16 to legendary STOL aircraft such as the AV-8 Harrier, while providing high levels of stealth and sensor fusion. Second, the F-35 is the most expensive weapons program in history and a key component of future airpower strategies for the United States and many of its closest allies. The Lightning II undoubtedly carries high expectations. However, despite its highly advertised performance, there is a catch. To understand why its availability and capabilities still fall short, despite record deliveries and popularity among numerous air forces, it’s necessary to look beyond production and examine the realities of global operations, maintenance, and complexity.

A Record Year For Deliveries, But Not A Record For Performance

In January 2026, Lockheed Martin confirmed that it had delivered 191 F-35s in 2025, the highest annual total in the program’s history. The achievement was widely celebrated as evidence that the production system had matured, that the certification issue for a Technology Refresh 3 (TR-3) configuration that had previously led to delivery delays was finally resolved, and that earlier supply-chain disruptions were largely under control. According to Breaking Defense, the company emphasized that three factories around the world – in Fort Worth (USA), Cameri (Italy), and Nagoya (Japan) – were now operating at a steady rhythm capable of supporting long-term demand.

In reality, this delivery surge reflects something more than industrial efficiency. It coincides with a period of heightened global insecurity, prompting many governments to accelerate fighter acquisitions. For countries facing increasingly contested airspace, particularly in Europe and the Indo-Pacific, the F-35 is viewed as a guarantee against future conflict. Deliveries, therefore, have become as much a strategic signal as a logistical achievement.

However, Pentagon watchdogs and independent analysts have repeatedly warned that delivery numbers alone do not reflect operational readiness or a successful deployment in a war zone. Several aircraft accepted in recent years entered service with known sustainment and software limitations. As a result, fleets have grown faster than the ability to keep them consistently mission capable. This gap continues to widen as more operators come online.

A Global Fighter With A Growing Circle Of Operators

Today, the F-35 is operated or on order by more than a dozen countries, making it the most widely adopted fifth-generation fighter in history. The United States remains the largest operator, with a total inventory of about 1,100 aircraft, flying all three variants across the United States Air Force, US Navy, and Marine Corps. But the aircraft’s true significance lies in its international footprint, which stretches from Northern Europe to the Western Pacific.

European operators such as the United Kingdom, Italy, the Netherlands, Norway, and Denmark have integrated the F-35 into their frontline squadrons, often as a direct replacement for aging fourth-generation fleets. In the Indo-Pacific, Japan, South Korea, and Australia view the jet as essential to maintaining air superiority in a region marked by rapid military modernization. Israel, meanwhile, has adapted its F-35s with indigenous modifications, making them suitable for highly specialized local operations, highlighting the aircraft’s flexibility and appeal. Other countries, such as Belgium, Finland, Poland, and some others, have placed orders or are awaiting delivery.

Current F-35 Operators (Active, With Aircraft in Service):

For many of these nations, buying the F-35 means a lot. The aircraft promises interoperability with US forces, shared logistics and technical support, and access to a continuous upgrade path. However, this interconnected operational network also means that sustainment challenges are rarely isolated. Problems encountered by one operator often ripple across the global fleet, requiring immediate response and solutions for all operators.

Low Capability Rates: The Program’s Most Persistent Weakness

Despite its advanced design, the F-35 continues to struggle with low mission-capable and full-mission-capable rates. As reported by The National Interest, a 2025 Pentagon Inspector General report found that the aircraft’s availability consistently fell well short of Department of Defense targets, with roughly half of the US fleet unable to perform assigned missions at any given time.

These figures give us a concerning view of aircraft performance. Capability rates directly influence how many aircraft commanders can depend on in a crisis. When availability stays around 50% (17% below the minimum performance requirement!), planners must either accept reduced combat power or compensate with extra aircraft and crews, resulting in an inefficient and costly fix. Military Watch Magazine has consistently pointed out that maintenance bottlenecks and spare-part shortages are key factors driving this issue.

What makes the issue especially troubling is its persistence across various operators. Similar concerns appeared in audits nearly a decade ago, suggesting that the challenge is structural rather than transitional. As the fleet grows, so too does the burden on sustainment systems that were never fully optimized for such scale.

Why These Problems Persist Despite Years Of Experience

The F-35’s availability challenges cannot be explained by a single flaw. Instead, they stem from the aircraft’s unprecedented complexity and the sustainment model built around it. From the beginning, it was designed as a flying sensor network; as a result, the jet relies heavily on software-driven systems that demand constant updates, diagnostics, and specialized maintenance. For example, Lockheed Martin alone employs an army of software and hardware engineers who create, update, and debug an impressive 8 million lines of code that F-35 systems rely on for successful operations, and not only technicians and mechanics who deal with aircraft parts.

A Pentagon audit examined by Inkstick Media noted that the logistics system supporting the F-35 remains overly centralized and insufficiently transparent, limiting the military’s ability to hold contractors accountable for performance shortfalls. Spare parts shortages persist, in part, because production priorities historically favored new aircraft over sustainment infrastructure. As a result, operators often resort to the last resource available: cannibalizing grounded jets to keep others flying.

As mentioned above, software development has also played a role. Delays in delivering fully mature software configurations have left some aircraft flying with restricted capabilities, further complicating maintenance and training. Unlike legacy fighters, where mechanical fixes often solved problems, the F-35’s issues increasingly require synchronized hardware, software, and data solutions, raising the bar for readiness and adding another factor to delays.

How Global Operators Experience The Readiness Gap

For air forces around the world, the question is not the F-35’s capability but how reliably that capability can be accessed. Operators routinely report that when the aircraft is available, it delivers exceptional situational awareness and survivability. The challenge lies in ensuring enough jets are ready at the same time to sustain operations.

In the United Kingdom, parliamentary reports have highlighted shortages of spare parts and trained personnel, limiting the number of F-35Bs that can be deployed from aircraft carriers or land bases simultaneously. Similar concerns have surfaced in Europe, where smaller air forces must balance high sustainment costs against limited defense budgets. Even well-resourced operators like Japan have acknowledged that maintaining availability requires constant coordination with US supply chains.

These experiences shed light on a shared reality: the F-35’s success depends as much on organizational adaptation as on technical refinement. Nations that invest heavily in local maintenance capacity, like Israel, and workforce development tend to fare better, but the learning curve remains steep.

A Program Still Taking Off, Not In Decline

The F-35 program has not fully recovered from the “teething troubles” that occurred early in its development and rollout. Currently, the F-35 faces a critical juncture. Record deliveries and increased global adoption confirm that it has become the de facto standard for allied fifth-generation airpower. However, ongoing shortfalls in capability remind operators that deploying advanced technology is only half the fight.

Improving availability and aircraft capabilities will require sustained investment in logistics reform, software stability, and maintenance infrastructure. For governments, the lesson is clear: buying aircraft is easy compared to sustaining them at scale. Some (costly) measures are necessary to ensure continuous sustainment, maintenance, and training. Until that balance is corrected, delivery records will continue to coexist with readiness concerns.

There is cautious optimism that the F-35’s readiness will improve as upgrades mature and sustainment models evolve. Whether those improvements arrive quickly enough to meet growing security demands will ultimately define how history judges the world’s most ambitious (and ambiguous) fighter program.