The U.S. Air Force has now denied taking delivery of any F-35A Joint Strike Fighters from the latest Lot 17 production batch without radars installed. This comes a day after TWZ published a detailed piece examining a recent unconfirmed report that the U.S. military has been receiving radar-less F-35s since last June due to issues tied to the new AN/APG-85 radar. Earlier this week, the F-35 Joint Program Office (JPO) had declined to confirm or deny whether that was the case, citing “enhanced security measures.”
“USAF F-35A lot 17 aircraft are delivering with APG-81 radars,” an Air Force spokesperson told TWZ today in an unprompted statement. “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.”
Since at least 2023, Northrop Grumman has been developing the APG-85 as a replacement for the existing AN/APG-81 radar used on all F-35 variants. The new radar is one part of the larger critical Block 4 upgrade package, which has been beset by delays and cost growth. Block 4 is also supposed to eventually include replacements for the Joint Strike Fighter’s AN/AAQ-37 Distributed Aperture System (DAS) and Electro-Optical Targeting System (EOTS), as well as a new electronic warfare suite and a host of other improved capabilities. In the past, the Air Force has described the electronic warfare package, which will be directly tied in with the APG-85, as a top priority.
“Lockheed Martin has been delivering F-35s to the military services since last June without radars, including all F-35As,” Defense Daily had reported last week, citing an anonymous source. “F-35 deliveries to U.S. units in the field since last June have had the APG-85 mountings, which do not fit the APG-81.”
“The radar-less F-35 deliveries have not affected sales to foreign partner nations which have the APG-81 on their jets, the source said,” that story added. “Without a radar, there had to be additional weight added in the nose for aircraft balance during flight. Radar-less F-35s have been able to fly, as long as they are accompanied by other F-35s, data linked and equipped with the APG-81, the source said.”
As mentioned, TWZ reached out earlier this week to the F-35 JPO with queries regarding the details in the Defense Daily piece.
“F-35 Lightning II aircraft are being built to accommodate the F-35 advanced radar (APG-85) for [the] U.S. Air Force, Navy, and Marine Corps,” an F-35 JPO spokesperson had told us in response. “Initial fielding for some F-35 aircraft is planned for Lot 17, which began delivery in 2025 and continues through September 2026.”
“Due to program security reasons, we are protecting any additional information with enhanced security measures,” the spokesperson added.
In addition, Defense Daily‘s report last week said it received a statement from the Air Force that was similar to the response we subsequently received from the JPO.
“This advanced radar [APG-85] will be compatible with all variants of the F-35 aircraft,” an Air Force spokesperson told that outlet. “Due to program security reasons, we are protecting any additional information with enhanced security measures.”
What has now changed regarding these “enhanced security measures” and why is unclear. There are still questions from our story yesterday that remain unanswered, including whether or not jets configured to accept the APG-85 can have the APG-81 installed for the time being. If modifications are required for this, it is not clear how substantial or invasive they might need to be. As we previously noted, a separate report last year from Breaking Defense had also pointed to a backwards compatibility issue and potential need to redesign the entire forward end of the fuselage to be able to accommodate both the APG-81 and the APG-85.
TWZ has followed up with the Air Force to see if more information may now be available.
As we detailed in our piece yesterday, there are additional questions about the general status of work on the APG-85 and the rest of the Block 4 upgrade package, and the timeline now for the delivery of any of those capabilities. The integration of the APG-85, as well as the new electronic warfare suite and many of the other improvements, are all directly intertwined with the need for more auxiliary power-generation and thermal cooling capacity. These demands are supposed to be addressed, at least in part, by an engine upgrade effort that is itself now running behind schedule.
The goal had previously been for F-35s with a complete suite of Block 4 improvements to begin arriving this year. A September 2025 report from the Government Accountability Office (GAO), a Congressional watchdog, said that those plans had been revised to focus first on a truncated portion of the upgrade package, but that schedule had still been set back at least five years.
The F-35 program continues to stare down growing costs associated with operating and maintaining the jets. Altogether, the total cost of the program from the start of development in the 1990s through the end of the type’s expected lifecycle in the 2070s, is now estimated to be approximtely $2.1 trillion. The JPO has stressed that inflation is expected to account for roughly half of that figure.
Altogether, even if F-35s are not being delivered now without radars, there are still significant challenges facing the Block 4 upgrade package and the rest of the Joint Strike Fighter program.
Contact the author: joe@twz.com