The F-35 Lightning II is among the aircraft that led the charge against Iran as part of “Operation Epic Fury,” with photos of the jets operating with near impunity over Iranian cities flooding the internet. However, these stealth jets are operating without the crucial TR-3 upgrade.
The US launched “Operation Epic Fury” on February 28 against Iran along with Israel. The two allies have delivered thousands of strikes and targeted Iran’s military infrastructure, including ballistic missiles, air defences, naval assets, command centres, and IRGC facilities.
The objective is to dismantle Tehran’s nuclear and ballistic missile capabilities, as consistently reported by the EurAsian Times.
Since the beginning of the conflict, the US and Israel have used the F-35 Lightning II aircraft for precision strikes as well as for suppressing enemy air defences (SEAD). An Israeli F-35I Adir also achieved a first air-to-air kill by downing a Yak-130 trainer.
The stealth capabilities of the F-35A enabled early ingress into Iranian airspace to suppress radar, integrated air defences, and command nodes, in coordination with cyber or space disruptions that enabled “blinding” of Iranian defence systems before broader strikes by other aircraft, such as strategic bombers.
Additionally, the F-35s also help provide real-time ISR (intelligence, surveillance, reconnaissance), sensor fusion for targeting, and delivery of guided munitions.
The F-35s stationed aboard the carrier wings of USS Abraham Lincoln and USS Gerald R. Ford have been spotted conducting both daytime and nighttime missions alongside F/A-18E/F Super Hornets and EA-18G Growlers.
These carrier-launched strikes have helped maintain pressure on Iran throughout the bombing campaign, enabling flexible, persistent airpower without relying solely on land bases that could be vulnerable to strikes.
The large-scale deployment of the F-35s in the ongoing conflict has prompted comparisons between the American-origin stealth aircraft and the Russian Su-57, with netizens noting that the Russian jet has never been seen flying over Ukraine in the four-year conflict.
In fact, F-35s were spotted flying low over Isfahan in central Iran, amid fresh pre-dawn airstrikes launched in the city on March 15. Earlier, the US F-35 jets also played a central role in “Operation Midnight Hammer”, launched by the US in June 2025, as earlier noted by EurAsian Times.
However, a new Pentagon report suggests that even as these jets fly missions over Iran, no new combat capability was added to them last year, and the efforts to update the F-35’s software have essentially “stagnated.”
No New Tech For F-35s
According to a report from the Pentagon Testing Office that was accessed by Bloomberg News, the latest F-35 upgrade, known as TR-3, which is meant to be integrated on jets like those participating in the Iran war, was “predominantly unusable” for most of last year due to stability problems, capability shortfalls, and ongoing discoveries of deficiencies.
This finding is concerning because the aircraft has been undergoing upgrades to the Technology Refresh-3 (TR3) configuration as part of a larger Block 4 modernisation plan.
The TR-3 avionics upgrade comprises updated integrated core processors, an aircraft memory system, and panoramic cockpit displays. In fact, some experts describe the TR3 as a brand-new laptop with a new display, improved graphics, and a new processor that speeds up operation and provides terabytes of memory and storage.
According to the Bloomberg report, the F-35 jets flying off the USS Abraham Lincoln aircraft carrier are equipped with the older TR-2 software.
Notably, Lockheed Martin began producing F-35s in the TR-3 version in the summer of 2023, but the government would not accept deliveries until TR-3 developmental testing was complete. Later, in July 2024, Lt. Gen. Michael Schmidt, Director of the Joint Program Office (JPO), authorised the resumption of deliveries, subject to assurances that the software was sufficiently stable in tests for safe flight operations and drills.
Nonetheless, despite the resumption of deliveries, the TR-3 is still undergoing developmental testing, and reports last year suggested that the aircraft delivered to the operators featured a “truncated” TR-3 configuration rather than a combat-capable TR-3.
According to the Pentagon report, the software improvements “continue to face challenges in delivering reliable, fully functional software” for rigorous combat testing prior to installation.
“The F-35 program continues to show no improvement in meeting schedule and performance timelines for developing and testing software, failing to deliver on the expectations of its agile development framework”, as “the process of addressing deficiencies and adding new capabilities has stagnated,” it emphasises.
It is pertinent to note that the TR3 upgrade is a crucial component in enabling new Block 4 mission-system capabilities to counter both air- and ground-based threats from adversaries. Although most of the Block 4 upgrades remain confidential, there is speculation that it includes a new active electronically scanned array (AESA) radar designated as AN/APG-85, a major upgrade to the jet’s Distributed Aperture System (DAS) and Electro-Optical Targeting System (EOTS), and the integration of new weapons.
Compared to the F-35’s current capabilities, the TR-3 upgrade is intended to enhance processing power by 37x and memory by 20x.
The delays in fielding TR-3 and, by extension, the Block 4 upgrades have persisted for years. This was also highlighted last year by the FY2024 Annual Report for the Office of the Director, Operational Test & Evaluation (DOT&E). The report stated that the program showed no improvement in meeting schedule and performance timelines for developing and testing software designed to address deficiencies and add new capabilities.”
“DOT&E assesses that dedicated operational testing of these aircraft will not occur until mid to late FY26, approximately two years after the configuration began delivery to the field,” it stated. Additionally, it noted that “challenges added with the TR-3 avionics upgrades, both in development and testing, have caused additional delays to the planned schedules for delivering capabilities in Block 4 for the aircraft in the TR-2 configuration.”
Initially, all 66 capabilities under Block 4 were scheduled to be fully deployed by 2026. This timeline was later pushed to 2029. However, a Government Accountability Office report in September 2025 warned that Lockheed would not be able to deliver the Block 4 upgrade, even with only a “subset of the original 66 … capabilities,” by 2031.
This does not augur well for the US Air Force (USAF) and its allies operating the jet, particularly as adversaries such as China continually upgrade their offensive capabilities. Moreover, there is a near-persistent threat from countries like Iran, as seen in real time.
Moreover, the delays have also raised concerns about additional costs on top of what is already the world’s most expensive fighter jet program, valued at around $2 trillion.
The US, for one, intends to purchase 2,470 aircraft for the Air Force, Navy, and Marine Corps. This comprises at least $1.5 trillion in long-term operations and maintenance expenditures over 77 years, as well as $485 billion in development and procurement, according to the GAO.
With plans to eventually retire the F-22 Raptor already underway, and the next-generation F-47 still years away from becoming combat-capable and achieving full technological maturity, there is a pressing need to upgrade the F-35 and make it more resilient against emerging threats. The TR-3 and Block 4 upgrades are crucial but delayed.
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