New F-35 Lightning II fighters could leave the factory floor without their next-generation APG-85 radar systems, according to a federal audit that documents persistent schedule slips and delivery delays across the jet’s modernization program. The finding raises a pointed question for the Pentagon: whether to keep shipping aircraft with older sensor hardware or hold production until the advanced radar is ready, a tradeoff with direct consequences for combat readiness and long-term costs.
Federal Audit Flags Delivery and Upgrade Delays
The U.S. Government Accountability Office laid out the problem in a report titled “F-35 Joint Strike Fighter: Actions Needed to Address Late Deliveries and Improve Future Development,” designated GAO-25-107632. The audit documents schedule slips, late deliveries, and systemic modernization risks tied to the Technical Refresh 3 (TR-3) and Block 4 upgrade packages. Those packages are supposed to bring a suite of new capabilities to the F-35, including integration of the APG-85 radar, which would replace the current APG-81 and significantly expand the jet’s ability to detect and classify airborne and ground-based threats.
The delays are not minor scheduling hiccups. TR-3 is the hardware backbone that makes Block 4 software possible, and the GAO found that both efforts have slipped well past their original timelines. Without TR-3 hardware installed and validated, Block 4 capabilities cannot function, and the APG-85 is one of the most prominent subsystems riding on that upgrade chain. The result is a cascading problem: jets rolling off the line may technically be new, but they could lack the sensor suite the program has been building toward for years.
In its broader work on weapons programs, the watchdog office has repeatedly warned that concurrency, developing and fielding systems at the same time, tends to magnify these kinds of risks. The F-35 modernization path, with overlapping hardware refreshes and software drops, fits that pattern. When one link in the chain slips, everything behind it begins to bunch up, and the program is left choosing between further delays or fielding jets that fall short of their promised configuration.
Why the APG-85 Matters for the F-35’s Edge
The APG-85 is not simply a faster version of the APG-81 it replaces. Built by Northrop Grumman, the radar is designed to give the F-35 a wider field of regard, better electronic warfare integration, and improved performance against advanced air defenses. For a fighter that relies on stealth and sensor fusion as its primary advantages, the radar is the single most consequential hardware upgrade in the Block 4 package.
Delivering jets without the APG-85 means those aircraft would fly with the older APG-81, a capable system in its own right but one designed over a decade ago. The gap matters most against peer adversaries fielding newer integrated air defense networks. Pilots in jets equipped with the legacy radar would have less situational awareness and fewer electronic attack options than what the Block 4 configuration promises. For the Air Force, Navy, and Marine Corps, each of which operates its own F-35 variant, the delay affects fleet-wide planning and training pipelines, because squadrons would have to juggle different sensor baselines for years.
The radar issue also interacts with the jet’s software-driven mission systems. Block 4 is meant to fuse data from the APG-85 with other onboard and offboard sensors, creating a more complete picture of the battlespace. If the radar is missing, the software cannot deliver its full value, and the aircraft’s role in joint operations is constrained. That undercuts one of the central rationales for the F-35: that it serves as a networked “quarterback” for other assets.
A $97.5 Million Bet on Keeping Radar Production Alive
The Pentagon has not been passive about the risk. A contract published by the Defense Department shows that Northrop Grumman Systems Corp. was awarded $97,500,000 to procure long-lead materials for APG-85 Lot Six radars. The contract is classified as an advanced acquisition, meaning the government is buying parts and components ahead of a full production order to protect the delivery schedule.
That dollar figure signals how seriously the program office treats the APG-85 as a schedule-critical item. Long-lead procurement is a standard tool for preventing supply chain bottlenecks from stalling major weapons programs, but it also reveals a tension. The government is spending nearly $100 million to keep radar materials flowing even as the broader TR-3 and Block 4 timelines continue to slip. If the jets themselves are not ready to accept the radar on schedule, those long-lead materials sit in storage, and the investment becomes a hedge rather than a solution.
From an industrial base perspective, the contract helps keep specialized suppliers engaged and production lines warm. Advanced radars rely on niche components and highly skilled labor, both of which can be difficult to reconstitute if demand suddenly drops. By locking in long-lead items, the Pentagon is effectively paying an insurance premium to avoid a cold restart later. But that insurance only pays off if the rest of the F-35 modernization ecosystem catches up.
The Retrofit Trap and Its Cost Implications
One scenario the GAO’s findings make plausible is that the Pentagon could accept new F-35s with the older radar and plan to retrofit them with the APG-85 later. This approach would keep production lines moving and avoid the political and contractual headaches of halting deliveries. But retrofits are almost always more expensive and time-consuming than installing hardware during initial assembly. Each jet that leaves the factory without the APG-85 would eventually need to return to a depot, be partially disassembled, and have the new radar integrated, a process that pulls the aircraft out of operational service for weeks or months.
That kind of retrofit cycle compounds across hundreds of airframes. The F-35 program already faces scrutiny over lifecycle costs, and adding a large-scale radar swap to the maintenance pipeline would increase both direct expenses and the indirect cost of reduced fleet availability. For allied nations that also operate the F-35, the same problem applies: their jets would either ship late or ship incomplete, and the retrofit burden would fall on an already stretched global sustainment network.
There is also a configuration management challenge. Fleets with mixed radar types demand different software loads, test procedures, and training syllabi. Units may have to maintain tactics for both APG-81 and APG-85 aircraft, complicating everything from mission planning to spare parts inventories. Over time, that fragmentation can erode some of the economies of scale that the multinational F-35 program was supposed to deliver.
What the GAO Recommends and What It Means
The detailed audit calls for specific actions to address the delivery delays and improve how the program manages future development. While the full text of its recommendations focuses on governance and schedule discipline, the underlying message is clear: the F-35 program office needs to stop treating delays as isolated incidents and start managing them as structural risks.
That distinction matters because the APG-85 situation is not an outlier. The GAO’s review describes a pattern in which modernization milestones slip, delivery timelines adjust, and the gap between what the jet is supposed to do and what it can actually do on delivery day keeps widening. The radar is the most visible example, but the same dynamic applies to other Block 4 capabilities that depend on TR-3 hardware being fully operational.
By highlighting these issues in a high-profile report, GAO is effectively pressing defense leaders to make harder choices sooner. That could mean slowing production until modernization hardware is ready, restructuring contracts to put more risk on industry, or prioritizing a smaller number of fully capable jets over a larger fleet of partially upgraded aircraft. None of those options is politically easy, but the audit suggests that deferring the decision simply pushes more cost and complexity into the future.
Reading Between the Contract Lines
Most coverage of F-35 delays focuses on software problems or Lockheed Martin’s production pace. The APG-85 story adds a different dimension: even when the government acts early to secure critical hardware, the broader program timeline can still undercut those efforts. The $97,500,000 Northrop Grumman award shows a program trying to buy its way out of schedule risk on one subsystem while grappling with deeper structural issues elsewhere.
Taken together, the audit findings and the radar contract sketch a familiar picture in modern defense acquisition. Advanced systems like the F-35 depend on tightly coupled hardware and software upgrades delivered on aggressive timelines. When those timelines slip, decision-makers face a constrained menu of imperfect choices: accept incomplete capability now and pay for retrofits later, or delay deliveries and absorb near-term readiness and political costs.
For the APG-85, that choice has not yet been fully resolved. But the warning signs are clear in the GAO’s analysis and in the Pentagon’s own contracting moves. Unless the program can realign its modernization schedule and better synchronize hardware and software delivery, more F-35s are likely to leave the factory in a limbo state, new airframes waiting on the radar that was supposed to define their next-generation edge.
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*This article was researched with the help of AI, with human editors creating the final content.
