The new radar is intended to replace the AN/APG-81, but the mounts for the APG-85 do not match those of the earlier system. Because the radars are purchased separately by the government, the delay lies with radar-maker Northrop Grumman rather than F-35 prime contractor Lockheed Martin.
F-35 Joint Program Office director Marine Corps Lt. Gen. Gregory Masiello told members of the Senate Armed Services Committee on June 23 that the only F-35s delivered without radars so far are six short takeoff and vertical landing F-35Bs for the Marines. The jets were produced earlier this year and began acceptance testing in February.
A spokesperson later confirmed that no Air Force or Navy aircraft had yet been delivered without radars. However, Air & Space Forces Magazine reported that both services will have to accept radar-less aircraft later this year.
Beginning with Lot 17, F-35 production aircraft are built with a unique bulkhead designed for the APG-85 radar. With that radar delayed and responsibility for the equipment falling to the government rather than Lockheed Martin, aircraft are being delivered now and the radars will be installed when available.
Aircraft without radars can be used for basic flight training, but not for combat training or missions. The Joint Program Office said the Pentagon “deliberately undertook a highly concurrent development and production program for advanced capabilities,” and said “this decision was made with full understanding of the risk of having production aircraft ready ahead of the capabilities.”
Air & Space Forces Magazine noted that similar delivery issues have occurred before, including with F-15 Eagles in the 1970s, when engine shortages required engines to be removed immediately after delivery and reused in other new aircraft. In the F-35 case, parts shortages and other problems contributing to readiness shortfalls have placed the program under additional scrutiny.
A Government Accountability Office report in June found that only about one in four F-35s was fully mission capable in 2025. The rate for aircraft able to carry out any of their missions was higher, at 44.1 percent, but still far below historical targets.
In testimony, Masiello said he would not “dispute their numbers or how they do it,” but argued that the GAO findings lacked context because of how F-35 readiness is calculated by the Joint Program Office. Using the JPO’s calculation, he said the mission-capable rate was higher, at 56 percent, while acknowledging that F-35s without radars are not fully mission capable.
The APG-85 radar is among several delayed upgrades included in the still-pending Block 4 configuration. Other changes include improved power and thermal management systems to help cool the radar, which will generate more heat than the existing APG-81.
Masiello said future F-35 systems will eventually require enough cooling to manage equipment consuming 62 to 80 kilowatts of power. That is more than double the 32 kilowatts consumed by existing hardware, which is also the limit of the current cooling system.
“Cooling really is what we’re looking at,” Masiello said. “There’s no margin, which as you know, is not a smart way to go.”
“So we have an incremental approach to increase that. And we have an ongoing program to look at a more systemic and affordable upgrade to the power thermal management across the program.”
The JPO funded development of a next-generation engine that could have provided more cooling power, but that effort was not funded after proving too costly. Masiello said cooling upgrades will not be ready until after 2031, when Pratt & Whitney’s upgraded engine core design is expected to be in production and fielded.
That engine will offer a “marginal increase” in cooling, but additional upgrades to the power and thermal management system will come several years later, Masiello said. Those improvements are expected to arrive in time for post-Block 4 upgrades.
Masiello deferred further answers about the APG-85’s capabilities and cooling requirements to the hearing’s classified session. The radar delay adds a near-term training-only limitation to aircraft deliveries while the broader F-35 modernization and readiness issues remain under review.
