The new US F-35s are being delivered without AN/APG-85 radar, with ballast as a replacement, revealing the industrial and technological limitations of the program.
Summary
Since mid-2024, the US Air Force has been accepting F-35As that have left the factory without operational radar, due to the unavailability of the new AN/APG-85 sensor planned to accompany the Block 4 upgrade and Technology Refresh 3 (TR-3) IT architecture. The aircraft are receiving a balancing weight in the nose to maintain center of gravity and flight stability, pending the subsequent installation of the final radar. This choice illustrates a dilemma: not interrupting the production rate of a strategic program involving more than 3,500 planned aircraft, while accepting that so-called “fifth-generation” fighters are, for the time being, incapable of fighting autonomously. The delays are due both to the complexity of the gallium nitride (GaN)-based AESA radar, which is more demanding in terms of energy and cooling, and to the stacking of TR-3/Block 4 upgrades, which are already experiencing difficulties. While export customers continue to receive F-35s equipped with the AN/APG-81 radar, the US forces are seeing their operational availability delayed and have to cope with a partially “hollow” fleet. This situation raises serious questions about the industrial governance of the program, the sustainability of its successive upgrades, and the credibility of the schedules announced to customers.
The new AN/APG-85 radar and its role in the F-35
The AN/APG-85 radar is designed to be the centerpiece of the F-35’s upgrade to the Block 4 standard, replacing or complementing Northrop Grumman’s current AN/APG-81 radar. It is a new-generation AESA (Active Electronically Scanned Array) radar, using gallium nitride (GaN) transceiver modules that are more powerful and efficient than previous technologies.
This sensor is expected to offer increased range, better resolution, and enhanced performance against stealthy airborne targets and modern surface-to-air threats. It is also designed as an electronic warfare tool, capable of jamming, detecting, and identifying enemy radars while performing traditional target detection and tracking functions. The US Air Force, US Navy, and US Marine Corps have announced that the AN/APG-85 will be compatible with all variants of the F-35 (A, B, and C), which implies deep integration into the airframe and mission systems.
This technological ambition comes at a cost: the electrical power required increases, as does the cooling requirements in the nose of the aircraft, areas that are already very constrained on a stealth fighter. The radar is therefore closely linked to the evolution of the TR-3 computer core, which must provide the computing and data processing resources essential to these new-generation sensors.
The drift of an already saturated integration schedule
The new AN/APG-85 radar was initially scheduled to appear in production batch 17, i.e., from 2025 for new F-35s destined for the United States. However, the roadmap has slipped: integration is now planned for batch 20, pushing back the sensor’s operational arrival to the end of the decade.
This delay does not come in a vacuum. The F-35 was already facing a partial freeze on deliveries in 2023-2024 due to difficulties in developing the TR-3 software, which is essential for unlocking Block 4 capabilities (new weapons, sensor enhancements, data fusion). US audit reports emphasize that full combat capability under TR-3 is not expected before 2026 at best, after several years of budget and schedule overruns.
The AN/APG-85 adds another stage to this modernization “rocket.” Testing has been delayed, in particular because the characteristics of the GaN radar require more extensive testing campaigns to validate reliability, thermal management, and integration with other sensors such as the Distributed Aperture System (DAS) and the Electro-Optical Targeting System
(EOTS). US officials are talking about efforts to “condense” and “truncate” certain test phases, a sign that political and operational pressure on the schedule is intense.
This accumulation of developments—TR-3, Block 4, APG-85—on a program already known for its complexity is undermining the entire industrial planning process. The slightest delay in a key subsystem has repercussions on the delivery of complete aircraft, creating a domino effect on the forces using them.
The solution for the F-35 without radar: ballast instead of sensors
Faced with delays, the question was simple: slow down production of a program exceeding the planned 3,000 aircraft, or accept incomplete aircraft. The Pentagon and Lockheed Martin chose the second option for US aircraft: F-35s now leave the factory with a nose structure designed for the AN/APG-85, but without the radar installed.
The problem is that the mechanical and electrical interfaces of the new radar are not compatible with those of the AN/APG-81, which means it is not possible to “go back” and install the old radar as a temporary solution. In order not to disrupt the aircraft’s center of gravity, which is essential for its stability, balancing weights are therefore positioned in the nose instead of the radar. In practice, the aircraft flies with an inert “dummy radar,” intended solely to replicate the weight and volume of the future sensor.
These F-35s can perform training flights and limited missions, relying on data links with other AN/APG-81-equipped aircraft or on the collaborative combat network infrastructure. In this configuration, the fighter behaves more like a stealthy data reception and fusion node than a fully autonomous platform, which is acceptable in peacetime but much more questionable in a contested environment.
Customers affected and those not affected by the problem
The decision to accept F-35s without radar primarily affects the US forces, starting with the US Air Force, which receives the majority of recent deliveries. Since the summer of 2024, aircraft destined for US units have been produced with the new nose architecture for the AN/APG-85, making them incompatible with the existing AN/APG-81.
On the other hand, export customers—initial partners such as the United Kingdom, Italy, the Netherlands, and Norway, or new customers such as Finland, Switzerland, and Poland—continue to receive F-35s equipped with the AN/APG-81 radar, which remains fully operational. The assembly lines are therefore segmented: some airframes are configured for the “old” architecture with APG-81, while others are configured for the future APG-85 integration intended primarily for the US forces.
This asymmetry creates a paradox: allied countries are now receiving complete F-35s with radar, while the United States is currently accepting aircraft that are potentially more “advanced” on paper, but in reality incomplete. In the medium term, Washington plans to equip the entire fleet—both American and allied—with the new AN/APG-85, but the retrofit procedures for earlier batches, as well as the precise timetable, have not been publicly detailed.
Operational impacts: misleading availability
Statistically, the current strategy allows Lockheed Martin and the Pentagon to post high delivery figures after the resumption of aircraft deliveries in July 2024 following the TR-3 problems.
The dashboards show a fleet that continues to grow in terms of the number of aircraft, but some of these aircraft do not have operational radar and cannot perform the missions for which a fifth-generation fighter is purchased.
Real availability is therefore deteriorating in terms of quality: an F-35 without radar remains useful for basic training, maintaining piloting skills, and certain experiments, but it cannot perform air superiority, complex ground attack, or enemy air defense suppression missions. In the event of a major crisis, these aircraft would be grounded or confined to secondary roles until radar could be installed.
This situation reinforces the idea of a “hollow fleet”: some of the aircraft counted as delivered and available do not have the expected level of equipment. For planners, this complicates the management of operational contracts, particularly in the US Air Force, which already has to contend with availability rates below targets on the existing F-35 fleet equipped with APG-81.
Revealing the structural weaknesses of the F-35 program
The episode of F-35s delivered without radar is not just a technical setback. It highlights several structural weaknesses in a program that has become the most expensive in Pentagon history, with a total life cycle cost estimated at over $1.7 trillion.
First, the logic of permanent incremental evolution—TR-1, TR-2, TR-3, Block 4, AN/APG-85, etc.—creates a system where the aircraft is in almost permanent development. Each new technological building block depends on other subsystems that are being redesigned, making schedules extremely sensitive to the slightest contingency on a critical component.
Second, industrial centralization around a limited number of players, with Lockheed Martin as the prime contractor and Northrop Grumman as the key radar supplier, concentrates risk. A delay on the AN/APG-85 immediately translates into major adjustments to overall production, due to a lack of redundancy or quick alternative solutions.
Finally, the tension between operational requirements and political imperatives of deliverability is evident. To avoid acknowledging further major delays, the program accepts incomplete aircraft, betting on the ability of industrial teams to make up for lost time during future retrofits. This approach postpones problems at the cost of increased fleet management complexity and modernization costs that remain largely opaque to taxpayers and foreign partners alike.
An inevitable debate on modernization choices
The decision to ship F-35s without radar forces the US military and its allies to clarify their priorities. Should priority be given to the rapid commissioning of “future-compatible” airframes capable of eventually integrating the AN/APG-85 and full Block 4 capabilities, even if it means going through several years with reduced availability? Or should they maintain more conservative configurations, based on the AN/APG-81 and stabilized software, at the risk of falling behind technologically compared to adversaries who are rapidly modernizing their own air defense systems?
This dilemma also affects customer countries. Those that are currently receiving F-35s equipped with the APG-81 have full and credible capability in the short term, but will likely have to finance and plan for an upgrade to the AN/APG-85 to remain aligned with the US fleet and benefit from future Block 4 capabilities.
Conversely, Washington is assuming the role of a full-scale test bed for the latest developments, at the cost of a riskier transition phase.
Beyond radar, this episode raises questions about the ability of major Western programs to integrate disruptive technologies at a pace compatible with operational and budgetary constraints. The F-35, often presented as the archetype of the “software” fighter, also demonstrates that the complexity of integration can, in the long run, temporarily deprive forces of the most basic capability: to see and strike on their own.
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