The U.S. Air Force has firmly denied that it has taken delivery of any F-35A Joint Strike Fighters from the latest Lot 17 production batch without radars installed, pushing back against an unconfirmed report that had stirred fresh controversy around the troubled Block 4 modernization effort.
The U.S. military had been accepting radar-less F-35s since June of last year due to integration challenges tied to the new AN/APG-85 radar. The report, originally cited by Defense Daily and attributed to an anonymous source, suggested that Lockheed Martin had been delivering F-35As configured for the new radar but without any radar fitted.
In an unprompted statement, an Air Force spokesperson rejected that assertion.
“USAF F-35A Lot 17 aircraft are delivering with APG-81 radars,” the spokesperson said. “The Air Force is working with the F-35 Lightning II Joint Program Office to deliver F-35s with APG-85 radars, and actual modernization plans, capabilities, and schedules remain classified to maintain program security.”
The statement marks a significant shift in tone from earlier official responses. Just days prior, the F-35 Lightning II Joint Program Office (JPO) had declined to confirm or deny whether radar-less aircraft were being delivered, citing “enhanced security measures” to protect sensitive program information.
The controversy began when Defense Daily reported that “Lockheed Martin has been delivering F-35s to the military services since last June without radars, including all F-35As.” According to the outlet’s anonymous source, jets delivered to U.S. units had been fitted with APG-85 mountings incompatible with the legacy AN/APG-81 radar.
The report further claimed that the aircraft were technically flyable despite lacking radars, provided they operated in formation with other F-35s equipped with functioning APG-81 systems and connected via secure data links. To compensate for the missing radar’s weight in the nose, ballast was reportedly added to maintain proper flight balance.
The source also indicated that foreign partner nations had not been affected, as their aircraft continued to use the APG-81 radar and were not transitioning immediately to the new APG-85.
The Air Force’s categorical denial that Lot 17 aircraft are arriving with APG-81 radars installed now directly contradicts the most striking aspect of that report. However, it leaves unresolved a host of technical and programmatic questions about how the service intends to transition to the APG-85 and when.
Since at least 2023, Northrop Grumman has been developing the AN/APG-85 active electronically scanned array (AESA) radar as a successor to the AN/APG-81 currently installed on all F-35 variants.
The APG-85 is a core component of the long-planned Block 4 upgrade package, a sweeping modernization effort intended to expand the F-35’s capabilities in electronic warfare, sensor fusion, weapons integration, and networking. The radar is expected to offer increased processing power, improved electronic attack performance, and greater resilience in contested electromagnetic environments.
Block 4 is also slated to introduce replacements for the F-35’s AN/AAQ-37 Distributed Aperture System (DAS), the Electro-Optical Targeting System (EOTS), and a revamped electronic warfare suite. The Air Force has previously described the electronic warfare enhancements—directly tied to the APG-85—as among its highest modernization priorities.
Yet Block 4 has been plagued by delays and escalating costs. Technical hurdles, software development challenges, and hardware constraints have repeatedly pushed back timelines. The integration of the APG-85, in particular, is intertwined with broader aircraft power and cooling limitations.
One of the central unanswered questions is whether F-35s configured structurally and electronically to accept the APG-85 can temporarily operate with the older APG-81 installed.
A separate 2024 report by Breaking Defense indicated that there could be backward compatibility issues between the two radar systems. That report suggested accommodating both radar types might require redesigning significant portions of the forward fuselage, potentially including structural modifications to mounting points, power supply architecture, and cooling pathways.
If the APG-85 mountings are indeed incompatible with the APG-81, as Defense Daily’s source claimed, that would complicate any interim solution involving radar swaps. The Air Force’s recent statement that Lot 17 aircraft are delivering with APG-81 radars suggests either that compatibility has been preserved or that aircraft are being built in a configuration still capable of accepting the legacy radar.
The service has not elaborated on what modifications, if any, are required to install APG-81 systems in jets structurally prepared for APG-85 integration.
Beyond structural compatibility, the APG-85’s integration is linked to broader power-generation and thermal management challenges within the F-35 platform.
The Block 4 package introduces significant new demands on the aircraft’s electrical and cooling systems. The addition of more advanced sensors, computing hardware, and electronic warfare capabilities requires greater auxiliary power and enhanced heat dissipation capacity.
To address this, the F-35 program has pursued an engine upgrade initiative aimed at improving power and cooling performance. However, that effort has also fallen behind schedule. Delays in delivering upgraded engine components capable of supporting the full Block 4 configuration have created a cascading effect on modernization timelines.
Originally, the goal had been to begin fielding F-35s equipped with a complete suite of Block 4 enhancements in 2025. However, a September 2025 report from the Government Accountability Office concluded that those plans had shifted toward delivering a reduced, or “truncated,” subset of Block 4 capabilities first.
Even that revised plan, the GAO found, had slipped by at least five years.
The recent shift in messaging from the JPO and the Air Force has raised questions about transparency.
Earlier statements from both organizations declined to provide details about radar integration, citing enhanced security measures to protect sensitive information. The Air Force’s new, unprompted assertion that Lot 17 jets are arriving with APG-81 radars appears to partially relax that stance—at least enough to rebut the claim of radar-less deliveries.
What prompted the change remains unclear. It is possible that public reporting and congressional interest increased pressure to clarify the matter. Alternatively, officials may have determined that confirming the presence of APG-81 radars did not compromise sensitive operational details about the APG-85’s development or integration schedule.
Regardless, significant aspects of the APG-85 timeline remain classified, including when initial operational capability will be declared and which units will first receive the upgraded radar.
The F-35 program is a multinational enterprise involving numerous partner and foreign military sales customers. According to Defense Daily’s report, foreign aircraft deliveries have not been affected by the alleged radar-less configuration, as partner nations continue to receive jets equipped with the APG-81.
Maintaining confidence among international operators is critical for the program’s long-term viability. The F-35 remains the backbone of airpower for multiple allied air forces, and any perception of instability in production or modernization could have strategic implications.
Thus far, there is no indication that partner deliveries have been delayed due to radar integration issues.
Even as the radar controversy unfolds, the F-35 program continues to grapple with its massive lifecycle cost burden.
The total projected cost of the program—from development in the 1990s through the anticipated end of service in the 2070s—is now estimated at approximately $2.1 trillion. According to the JPO, roughly half of that figure is attributed to inflation over the decades-long lifecycle.
Operating and sustainment costs remain a major concern for the Air Force and other services. Efforts to reduce cost per flight hour have yielded mixed results, and maintaining a growing fleet of advanced stealth aircraft poses ongoing logistical and budgetary challenges.
Even if the Air Force’s denial settles the question of radar-less deliveries for now, the broader issues surrounding Block 4 modernization remain unresolved.
The APG-85 radar is not merely an incremental improvement; it represents a significant step in adapting the F-35 to increasingly contested environments where electronic warfare and sensor dominance are critical. Delays in fielding that capability could affect the aircraft’s competitive edge against near-peer adversaries.
Moreover, the intertwined challenges of radar integration, power generation, cooling capacity, and engine upgrades underscore the complexity of modernizing a fifth-generation fighter at scale.
For now, the Air Force insists that its newest F-35A aircraft are arriving fully equipped with APG-81 radars. But as the program transitions toward the APG-85 and the broader Block 4 suite, scrutiny is likely to intensify.
The F-35 remains the most ambitious and expensive fighter program in history. Its future effectiveness hinges not only on maintaining production rates but also on successfully delivering the advanced capabilities promised under Block 4—on time and within budget.
Whether the recent radar controversy proves to be a misunderstanding or a symptom of deeper integration challenges, it has once again highlighted the delicate balance between program security, transparency, and operational readiness in one of the Pentagon’s most consequential weapons systems.
