U.S. F-35A fighter jets validate B61-12 nuclear bomb for NATO deterrent.

Recent B61-12 stockpile flight tests from U.S. Air Force F-35A fighters at Tonopah Test Range in Nevada have validated the bomb’s performance and reliability using inert test shapes. The results mark a shift from production to long-term sustainment of the air-delivered leg of NATO’s deterrent on a fifth-generation platform, with direct implications for European nuclear sharing and future force planning.

Sandia National Laboratories and the U.S. National Nuclear Security Administration said on 13 November 2025 that a series of B61-12 stockpile flight tests from F-35A Lightning II aircraft at Tonopah Test Range confirmed the weapon’s performance and reliability in operationally realistic conditions. Conducted from 19 to 21 August with aircraft and crews from Hill Air Force Base in Utah, the event used instrumented, non-nuclear B61-12 test shapes dropped from the fighter’s internal bays and tracked to impact, closing a key milestone that follows the formal completion of the B61-12 Life Extension Program in December 2024.
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Recent B61-12 test drops from U.S. F-35A fighters at Tonopah confirm nuclear stockpile performance and move NATO’s air-delivered deterrent into a sustainment phase. (Picture source: US DoD)

The B61-12 nuclear gravity bomb (B61-12) is the latest version of the B61 family, combining refurbished warhead components with a new guided tail kit. Open sources describe four selectable yields ranging from 0.3 to 50 kilotons, which allows planners to tailor the desired effect through accuracy rather than depending on higher yields. The new tail section incorporates an inertial guidance unit that keeps impact error within a reduced radius and provides the bomb with limited glide capacity, decreasing the yield required to hold hardened targets at risk. With an overall length of about 3.6 meters and a mass of roughly 825 kilograms, the weapon remains compatible with existing storage, handling, and aircraft interface standards while replacing several earlier B61 variants in a single configuration managed under the Life Extension Program (LEP).

In August, engineers from Sandia, teams from the National Nuclear Security Administration (NNSA), and United States Air Force personnel focus on B61-12 test shapes across the full mission profile. Inert rounds are loaded into the internal bays of the F-35A Lightning II (F-35A) at Hill Air Force Base (Hill AFB), flown to the Tonopah Test Range (TTR), released in different profiles and tracked by telemetry until impact on the Nevada range. The series includes an initial thermal conditioning of a B61-12 carried on an F-35A before release, exposing the bomb casing and electronics to controlled temperature cycles that reproduce operational carriage conditions. The combination of environmental and flight testing is one of the pillars of the surveillance framework that allows NNSA to certify stockpile reliability without nuclear testing while also training the aircrews assigned to the mission.

The F-35A Lightning II (F-35A) reaches this stage after its certification in October 2023 as the first fifth-generation fighter authorized to deliver the B61-12 in the nuclear role, several months before the schedule announced to North Atlantic Treaty Organization (NATO) capitals. The aircraft combines the AN/APG-81 active electronically scanned array radar (AN/APG-81) with an electro-optical targeting system, a distributed infrared sensor suite, and the AN/ASQ-239 electronic warfare system (AN/ASQ-239), fused into a single tactical picture. Secure data links, including Link 16 and the Multifunction Advanced Data Link (MADL), feed this picture into the joint Recognised Maritime Picture/Common Operational Picture (RMP/COP). For the nuclear mission, internal carriage of the B61-12 preserves low observability, while the mission computers preload target data and release parameters so that the aircraft can operate under strict emission control (EMCON) when flying against integrated air defence systems.

At the tactical and operational levels, the combination of B61-12 and F-35A provides the Alliance with a dual-capable aircraft that gradually replaces fourth-generation fighters. The accuracy of the guidance system and the choice of yield reduce the number of aircraft required to treat a given target set and limit exposure to opposing fires. The AN/APG-81 active electronically scanned array radar (AN/APG-81) and the fused sensor suite enable the F-35A to map threat emitters, locate mobile launchers and identify gaps in radar coverage without relying only on external cueing, while the Multifunction Advanced Data Link (MADL) and Link 16 give patrols a shared view of the air and surface situation in near real time. In a crisis, this mix of low observability, networking, and nuclear delivery capacity offers allied command structures additional options for graduated signalling, from dispersal and heightened alert postures to forward deployments and training flights conducted in allied airspace.

Confirmation of B61-12 and F-35A compatibility at Tonopah takes place as Russia’s war against Ukraine, repeated nuclear references from Moscow and renewed investment in air-delivered nuclear weapons on both sides revive debate over NATO nuclear sharing arrangements. For European allies adopting the F-35A as their next dual-capable aircraft, the August tests close the final technical step before B61-12 deployment to bases assigned a nuclear role. They also intersect with broader decisions, such as the United Kingdom’s choice to acquire F-35A aircraft configured to carry the B61-12, to diversify and modernise national deterrent portfolios. For competitors and partners, the message is that the Western defence industrial and technological base (BITD) is completing the Last Production Unit (LPU) cycle for the B61-12 and shifting toward long term sustainment of an air-delivered deterrent adapted to contested airspace.