The situation created by delays in the development of the AN/APG-85 radar, which has officially been under development since early 2023, will directly impact the U.S. Air Force (USAF), which will receive F-35A fighters without radars over the coming months. The problem affects all three U.S. service branches that operate the Lightning II, since the new sensor was intended to replace the AN/APG-81 and be progressively incorporated into Lot 17 aircraft, whose deliveries began in 2025 and will continue through September 2026.
The first aircraft affected by this situation was an F-35B, which in late February carried out an acceptance flight with ballast in its nose instead of the advanced radar. The test flight, conducted at Lockheed Martin’s facilities in Fort Worth, Texas, was a necessary step to allow the new radar-less aircraft to be temporarily accepted by the armed forces, given that the AN/APG-85 units are considered government-furnished equipment under the contract.
According to sources linked to the program, several F-35B units have already flown without radar in recent weeks, although their delivery has not yet taken place. The situation could continue for much of the year and possibly into the next, while Northrop Grumman completes development of the AN/APG-85 AESA sensor, designed to replace the AN/APG-81 and enable the full integration of the Block 4 upgrade package. Neither Lockheed Martin nor Northrop Grumman issued statements and instead referred inquiries to the F-35 Joint Program Office (JPO), which did not respond.
The JPO had previously stated that Lot 17 aircraft would continue to arrive with the APG-81 radar until the new system became available. The U.S. Marine Corps (USMC) acknowledged that the Block 4 modernization strategy — which includes the AN/APG-85 — depended on the concurrent development of multiple components, which led to disruptions in the schedule. “The Department of War deliberately undertook a highly concurrent development and production program for Block 4 capabilities, including the APG-85,” said USMC spokesman Captain Jacob Sugg. “Officials made this decision understanding the risk of having production aircraft ahead of Block 4 capabilities.”
Industry experts pointed out that halting F-35 production to wait for the radar would have had even greater consequences. Heather Penney, director of studies at the Mitchell Institute for Aerospace Studies and a former F-16 pilot, stated that delivering aircraft without radar is “the least harmful option” for keeping the line active. She explained that interrupting production would lead to the loss of skilled labor and deterioration in industrial processes, which would delay the program even further.
Penney recalled that a similar situation occurred in the 1970s, when the first F-15 Eagle aircraft were delivered without engines because of delays by manufacturer Pratt & Whitney. Unlike that case, the F-35 faces an additional challenge: the bulkhead where the radar is mounted was redesigned for the AN/APG-85 and is not compatible with the AN/APG-81, which prevents a direct substitution. Each radar requires its own software, and its integration into the aircraft’s architecture is not interchangeable.
Even without radar, the F-35s from the new lot will be able to carry out basic training missions and support the transition of squadrons moving from platforms such as the A-10 or the F-16. Penney explained that these aircraft are not rendered inoperative, since the Lightning II has a distributed electro-optical vision system and extensive data-link capabilities that allow it to receive radar information from an accompanying F-35 or from other airborne battle-management aircraft such as the E-3 Sentry. “It is a fully operational asset,” she said. “It is not ideal and does not provide the full capability, but with a mixed formation the lack of radar can be compensated for.”
Images for illustrative purposes.
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