The U.S. military has confirmed that at least six F-35 Joint Strike Fighters have been accepted into service without their primary radar systems installed, highlighting growing challenges surrounding the F-35 program’s ambitious Block 4 modernization effort. The revelation underscores the increasingly complex technical and logistical hurdles facing what remains the world’s most expensive and technologically advanced fighter aircraft program.
The disclosure came during a Senate Armed Services Committee hearing this week, where Marine Corps Lt. Gen. Gregory Masiello, head of the F-35 Joint Program Office (JPO), acknowledged that six aircraft delivered to the U.S. Marine Corps were accepted without radar systems because the next-generation AN/APG-85 radar is not yet available.
The confirmation marks the first official acknowledgment that operational F-35s have entered military inventories lacking one of the aircraft’s most important combat systems.
The issue emerged during questioning by Senator Mark Kelly of Arizona, a former naval aviator and astronaut, who pressed military officials about persistent concerns surrounding F-35 readiness rates.
Kelly referenced a recent Government Accountability Office (GAO) report that found the average full mission capable (FMC) rate across all F-35 variants had declined significantly, falling from 38 percent in Fiscal Year 2020 to just 25 percent in Fiscal Year 2025. Full mission capable status refers to aircraft that are able to perform all assigned combat missions.
Although the Joint Program Office disputes the methodology used by the GAO to calculate readiness, Kelly highlighted the discrepancy between government oversight figures and military assessments.
During the exchange, Kelly noted that many aircraft remain unavailable for missions and then raised reports that the Marine Corps had accepted fighters without radar systems.
“We have accepted six aircraft for the Marine Corps that do not have a radar installed,” Masiello confirmed.
When Kelly asked whether the situation was caused by a shortage of AN/APG-85 radars, Masiello answered affirmatively.
The aircraft are widely believed to be F-35B short takeoff and vertical landing variants, although Masiello did not explicitly identify the variant during the hearing. The Marine Corps is currently the only U.S. military branch that operates the F-35B, though it also flies the carrier-capable F-35C.
The radar shortage stems directly from delays affecting the AN/APG-85, a next-generation active electronically scanned array (AESA) radar being developed by Northrop Grumman.
The AN/APG-85 represents one of the most important components of the broader Block 4 modernization package, a sweeping upgrade initiative intended to keep the F-35 competitive against evolving threats well into the coming decades.
Military officials describe Block 4 as essential for maintaining air superiority against increasingly capable adversaries. The modernization effort encompasses new sensors, enhanced electronic warfare systems, improved computing power, expanded weapons integration, and advanced networking capabilities.
However, the program has suffered repeated delays and escalating costs.
According to budget documents released earlier this year, the first production AN/APG-85 radars are not expected to be delivered until April 2028. While that date actually represents an improvement over previous schedules, it remains years later than originally envisioned.
The delay has created an unusual situation in which newly manufactured aircraft are rolling off production lines before critical systems designed for them are ready.
Military officials have defended the decision to continue production despite incomplete modernization components.
According to Marine Corps representatives, the Department of Defense deliberately chose a highly concurrent approach in which aircraft production and technology development proceed simultaneously. Officials argue that producing aircraft configured to eventually receive Block 4 upgrades is preferable to continuing construction of older Block 3 configurations that would later require extensive and costly retrofits.
The strategy, however, comes with clear risks, including the current reality of delivering combat aircraft lacking radar systems.
The radar is one of the most important systems aboard any modern fighter aircraft, and its absence significantly affects operational capability.
Current F-35 variants rely on the AN/APG-81 AESA radar, which provides air-to-air tracking, air-to-ground targeting, synthetic aperture radar mapping, reconnaissance functions, and electronic warfare capabilities.
Developed using technologies originating in the 1990s, the AN/APG-81 remains highly capable and has been combat proven. Nevertheless, military planners view the AN/APG-85 as necessary to counter future threats.
Although details remain classified, the new radar is expected to offer substantial improvements in detection range, processing power, target tracking, electronic attack capabilities, and resistance to enemy countermeasures.
Industry observers also believe the system incorporates newer gallium nitride semiconductor technologies that enable greater performance while improving efficiency and thermal management.
The AN/APG-85 is expected to function not merely as a radar but as an integrated sensor node deeply connected with the aircraft’s electronic warfare systems, communications architecture, and mission computers.
As a result, delays affecting the radar could have cascading effects across multiple Block 4 capabilities.
The acceptance of radarless F-35s raises significant questions about how the aircraft will be used until replacement systems become available.
During the hearing, Senator Kelly openly questioned whether aircraft lacking radars could be considered fully mission capable.
“I don’t think I would count them as fully mission capable,” Masiello admitted.
Kelly responded by saying he could not imagine circumstances in which an F-35 without a radar could qualify as fully mission capable, a point Masiello did not contest.
Despite lacking radars, the aircraft are not completely unusable.
The F-35 was designed around extensive sensor fusion and networking capabilities. Through the Multifunction Advanced Data Link (MADL), aircraft can share information among formations in real time.
In practice, this means radar-equipped F-35s can provide targeting and situational awareness information to aircraft operating without their own radar systems.
Additionally, pilots retain access to information from passive sensors, including infrared search systems, electronic support measures, and external data provided through Link 16 networks.
However, significant limitations remain.
Aircraft without radars must depend heavily on nearby aircraft or external platforms for targeting information. This dependence reduces tactical flexibility and may increase operational risk during high-threat missions.
The absence of radar capability also diminishes the aircraft’s ability to independently detect, identify, and engage threats.
Perhaps more importantly, the radar plays a crucial role in the F-35’s electronic warfare architecture.
Modern AESA radars can perform electronic attack functions by transmitting highly focused energy beams to disrupt or deceive enemy sensors. Without a radar, an F-35 loses a substantial portion of its electronic warfare capability, reducing its ability to protect itself and other friendly forces operating nearby.
The AN/APG-85 delay is only one aspect of a broader challenge confronting the F-35 program.
During the same Senate hearing, lawmakers explored growing concerns about the aircraft’s power generation and thermal management systems.
The issue centers on whether the F-35 can adequately cool and power all of the advanced technologies planned under Block 4.
According to Senator Kelly, current aircraft generate roughly 30 kilowatts of cooling capacity. Existing Block 4 requirements demand approximately 32 kilowatts, effectively consuming nearly all available capacity.
Masiello acknowledged that future requirements could ultimately reach between 62 and 80 kilowatts.
That leaves little room for growth.
“There’s no margin,” Masiello told lawmakers, explaining that operating complex military systems without reserve capacity is not an ideal long-term strategy.
The Joint Program Office is pursuing incremental improvements while simultaneously studying larger upgrades to the aircraft’s Power and Thermal Management System (PTMS).
Officials anticipate an engine core upgrade around 2031 that will provide modest increases in cooling and electrical generation capability. More comprehensive power and thermal upgrades are expected later.
Although Masiello stated that AN/APG-85 integration would not require those future improvements, questions remain regarding how much capability can be fully utilized before enhanced cooling systems become available.
The discussion highlighted another recurring challenge for the F-35 program: the growing demands imposed by increasingly sophisticated onboard systems.
As sensors, computing power, electronic warfare capabilities, and networking technologies evolve, the aircraft’s infrastructure must continually expand to support them.
The radar delay is part of a broader pattern affecting Block 4 modernization.
According to the Government Accountability Office, portions of the program remain approximately five years behind schedule.
The original vision called for aircraft equipped with the full Block 4 capability package to begin entering service around this period. Instead, key elements continue to face development and integration challenges.
Beyond the AN/APG-85 radar, Block 4 includes plans for upgraded versions of the F-35’s Distributed Aperture System (DAS) and Electro-Optical Targeting System (EOTS), along with a completely new electronic warfare suite.
The modernization package will also support additional weapons, expanded sensor capabilities, enhanced data processing, and improved networking functions.
Military officials consistently describe the electronic warfare upgrades as among the most important components of the program, particularly given increasingly sophisticated air defense systems being fielded around the world.
Many of these future capabilities depend upon successful integration of the AN/APG-85 and supporting infrastructure upgrades.
Consequently, radar delays threaten to influence multiple areas of the modernization roadmap.
The radar issue emerges against a backdrop of broader concerns about fleet readiness.
The F-35 program continues to struggle with maintenance demands, sustainment costs, and spare parts availability.
Masiello acknowledged before lawmakers that inventory shortages have become a significant contributor to readiness problems.
According to the JPO director, the issue is less about flaws within the aircraft itself and more about insufficient investment in spare parts inventories as fleet size expanded rapidly.
The number of operational F-35s has grown substantially across the Air Force, Navy, Marine Corps, and international partner nations. However, logistics systems have not always kept pace with increasing demand.
Officials now hope future budget increases will help replenish inventories and improve aircraft availability.
Nevertheless, readiness remains a central concern for policymakers overseeing a program expected to remain in service through the 2070s.
The F-35 remains the largest and most expensive military aviation program in history.
As of last year, total lifecycle costs were estimated at approximately $2.1 trillion, covering development, procurement, operations, maintenance, and modernization throughout the aircraft’s projected service life.
Program officials emphasize that the figure encompasses thousands of aircraft and decades of operations, with inflation accounting for a significant portion of the projected expense.
Even so, lawmakers continue to scrutinize costs, schedules, and readiness performance.
The revelation that radarless aircraft are now entering military service is likely to intensify that scrutiny.
While defense officials maintain that the decision was a calculated and deliberate risk intended to accelerate future modernization, critics may view the development as evidence of a program increasingly strained by technical complexity and ambitious requirements.
For now, at least six Marine Corps F-35s are flying without the radar systems they were designed to carry. With production AN/APG-85 radars not expected until 2028, and broader Block 4 upgrades still facing delays, the unusual situation may persist for years.
The development illustrates both the extraordinary ambition of the F-35 program and the significant challenges involved in continually evolving a fifth-generation fighter to meet future battlefield demands.
