Israel Custom Built its F-35s For War with Iran: How Have Modifications Enhanced Them?

As the Israeli Air Force’s F-35 fleet continues to play a central role in the country’s <a href="https://militarywatchmagazine.com/article/iran-top-air-defence-bavar373-f35-shootdowns" target="_blank">air campaign against Iran</a>, which was initiated in the early hours of June 13 with the launch of massive air and missile strikes on the country, assessments of the extensive customisation of Israel’s unique variant of the aircraft have gained growing significance. Although the F-35 has received orders from over two dozen services across the world, the Israeli Air Force is the only foreign service which has gained permission to extensively customise the aircraft and integrate indigenous avionics. This was insisted on by the Israeli Defence Ministry largely due to concerns that the F-35’s stealth capabilities could not be relied on exclusively to ensure the aircraft’s survivability, as improvements in radar, infrared tracking, and data sharing technologies would over the fighter’s lifetime increase adversaries’ ability to target it. Although the F-35’s electronic warfare suite is by far the most formidable deployed by a Western fighter aircraft, not only are the suites on export variants of the fighter downgraded, but the ability to integrate indigenous systems also allows them to be continuously modernised while exploiting the Israeli defence sector’s considerable expertise in the field.&nbsp;<img src="https://militarywatchmagazine.com/m/articles/2025/06/16/article_684f6ff5eae3b2_13103620.jpeg" title="Israeli Air Force F-35I">The Israeli Defence Ministry ordered the first batch of 19 F-35s on October 7, 2010, with subsequent orders in February 2015 and August 2017 bringing the number to 50, which was sufficient to equip two squadrons based at <a href="https://militarywatchmagazine.com/article/strike-completely-destroys-f35-base" target="_blank">Nevatim Airbase</a>. Aircraft initially delivered in 2016 were less heavily customised, with indigenous Israeli avionics including only the command, control, communications and intelligence systems. With the United States having proved highly reluctant to allow Israel to more deeply modify the F-35, a system was developed under which Israeli avionics would be added on top of the unmodified avionics of the aircraft. This process was summarised by General Manager of the Lahav Division at Israel Aerospace Industries, Benni Cohen, who stated: “It's open architecture, which sits on the F-35's central system, much like an application on your iPhone. So it doesn't change anything in the aircraft itself, but it gives the Israel Air Force the most advanced and adaptable processing capabilities with relative independence of the aircraft manufacturer.” This “introduces a new level of freedom for the IAF [Israeli Air Force], as it paves the way for additional advanced capabilities to be embedded in the F-35I in the future,” he concluded.<img src="https://militarywatchmagazine.com/m/articles/2025/06/16/article_684f71150303d4_01227849.jpg" title="F-35 Production at Fort Worth, Texas">To support Israeli efforts to customise its F-35s, the fighter program’s primary contractor Lockheed Martin built a unique testbed aircraft to allow local modifications to be trialled in Israel. Israeli Air Force Lieutenant Colonel Shlomy Binder, who headed testing efforts, observed that the testbed “will enable us to begin the work of upgrading the capabilities of this aircraft so that it answers our special operational requirements,” including for “using the unique weapon systems made by Israeli industry.” One of the most significant benefits which Israel gained was the ability to maintain the aircraft without using the American ALIS logistics system or its successor the ODIN system, which not only avoided considerable problematic issues with the former, but also provided much greater operational autonomy and made the Israeli F-35 fleet the only one which could not be easily <a href="https://militarywatchmagazine.com/article/german-policymakers-concerned-american-kill-switch-disable-f35" target="_blank">shut down from the U.S.</a>&nbsp;With Israel <a href="https://militarywatchmagazine.com/article/israel-contract-third-f35-squadron">increasing F-35 orders</a> to 75 fighters in June 2024, the benefits for the country’s defence sector of providing both ‘add ons’ for the avionics suites and a high degree of domestic servicing have been significant.&nbsp;<img src="https://militarywatchmagazine.com/m/articles/2025/06/16/article_684f70177273b8_44299242.jpeg" title="Natanz Nuclear Facility After June 13 Israeli Air Strikes">Beyond changes to avionics, a major Israeli requirement for the F-35 fleet was to extend the range of the fighters to facilitate penetration strikes of Iranian territory without reliance on aerial refuelling. The means by which this has reportedly been achieved remains uncertain, with one possibility being the integration of conformal fuel tanks, and another being the jettisoning of non-stealthy external fuel tanks before approaching Iranian airspace, and consuming all fuel from these tanks in the first part of the flight. Although Israeli air operations initiated on June 13 have reportedly seen the country benefit from extensive aerial refuelling support from countries across the Western world, had such support not been provided, Israel’s own tanker fleet would have been hard pressed to extend the range of its large F-35 and F-16 fleets to facilitate strikes on Iran. The expected growing vulnerability of tankers as Iran begins to <a href="https://militarywatchmagazine.com/article/can-su35-delivery-turn-tide-iran-favour-russia-jets-onorder" target="_blank">operationalise modern fighter aircraft </a>equipped with <a href="https://militarywatchmagazine.com/article/longest-ranged-aam-performs-ukraine-su57" target="_blank">very long range air-to-air missiles</a> provided a further incentive to develop this capability.&nbsp;Israel’s F-35 fleet was procured and heavily customised specifically with operations against Iran and Syria in mind, with&nbsp;the&nbsp;<a href="https://militarywatchmagazine.com/article/netanyahu-details-israeli-air-turkish-takeover" >fall of Syria</a>&nbsp;to Turkish and&nbsp;<a href="https://www.timesofisrael.com/idf-chief-acknowledges-long-claimed-weapons-supply-to-syrian-rebels/" >Israeli backed insurgents</a>&nbsp;in December 2024&nbsp;having left Iran as the sole major target. Although Iranian sources have <a href="https://militarywatchmagazine.com/article/iran-shoots-down-third-f35-captures-second-pilot" target="_blank">claimed shootdowns</a> of three Israeli F-35s by local air defences, the ability to launch penetration strikes deep into very heavily defended airspace with such a conservative loss rate has reflected well on the F-35’s survivability. Losses more than an order of magnitude higher would have been likely had any other Western fighter class been relied on. The extent to which Israel’s customisation of the F-35 has contributed to this survivability, however, remains uncertain.&nbsp;