The F-35 Lightning II was used in August 2025 to successfully evaluate three B61-12 test assets during a multi-day test campaign.
Sandia National Laboratories and the National Nuclear Security Administration (NNSA) just disclosed that a B61-12 stockpile flight test campaign took place in August 2025. The successful testing was conducted at Tonopah Test Range, Nevada, with support and aircraft generation from Hill Air Force Base, Utah.
Stockpile Flight Test
Sandia says the tests were conducted on Aug. 19-21, and saw three inert units of the B61-12 nuclear gravity bomb were successfully carried and dropped by an F-35 during that timeframe. A photo and video released together with the statement show the F-35 carrying two B61-12s in its weapon bays, although it is unclear if a dual drop was also conducted.
The agency says the test yielded positive results as aircraft and marking “a significant milestone in evaluating the weapon’s performance.” This milestone follows a multiyear life extension program for the B61 completed by the NNSA in late 2024 with the production of the B61-12 Last Production Unit (LPU), which allowed to extend the bomb’s service life by at least 20 years.
These were “the only B61-12 stockpile flight tests of joint test assemblies on an F-35 aircraft, solidifying the end-to-end reliability of the aircraft, crews and weapon system during missions.” Stockpile flight testing is part of the NNSA’s stockpile surveillance and assessment, and uses Joint Test Assemblies that remove the nuclear package and replace it with telemetry systems to ensure the U.S. nuclear weapons stockpile remains safe, secure, and effective.
Additionally, the tests also included “the first-ever thermal preconditioning of a joint test assembly for carriage on an F-35 aircraft prior to its release, validating B61-12 environmental requirements in a real-world combined environment.” In fact, as shown in the video, the B61-12 JTA was transported in a special container connected to an environmental control system.
“These B61-12 F-35A stockpile flight tests and captive carry flight test were the capstone accomplishment of a tremendous amount of planning and effort by those who were involved across not only Sandia, but many other agencies,” said Sandia’s Jeffrey Boyd, surveillance lead for the B61-12 and B61-13. “In addition, these B61-12 stockpile flight tests represent the completion of the most B61-12 flight testing surveillance scope in a year to date and the most in a given year for the foreseeable future.”
Tonopah Test Range’s Manager Brian Adkins oversaw the tests at the range and praised the work of the team involved. “Expedient coordination by the entire test team resulted in two successful days of testing to evaluate three test assets,” Adkins said.
The B61-12
A variable yield design, with reported yields between 0.3 and 340 kilotons, the B61 is an air-delivered family of tactical nuclear weapons developed by the USA since December 1962 in 14 iterations. The B61-0, the first version, started production in 1967, and since then around 3,155 B61 bombs have been produced, with an estimated 540 in service and 415 in reserve in 2012.
Around 400 B61-12 were then planned, converted from previous B61-4 (a version that started production in 1979) and using components from older warheads, to serve alongside the around 50 B61-11 bunker buster nuclear weapons. The weapon was planned to become the only remaining gravity delivered nuke in the inventory, at least until the B61-13 was announced.
Originally an unguided weapon, the basic B61 had a streamlined casing 11 feet and 8 inches long (3.56m) and a diameter of 13 inches (33 cm) able to withstand supersonic flight. Weighting around 700 pounds (just over 300 kg), the B61 was designed to be carried by tactical airplanes of the United States Air Force and of NATO partner nations, thanks to the NATO Nuclear Weapons Sharing Program.
The upgraded weapon carries a low-yield nuclear warhead with four yield options and is delivered in either ballistic or guided-gravity drop modes, thanks to a new Boeing-built tail assembly that includes an Inertial Navigation System (INS) precision-guidance package and two spin rocket motors.
The guided tail-kit assembly allows both improving the accuracy and gifting the B61 with some standoff range. Reportedly, the B61-11 has an accuracy of 110-170 meters, while the guided B61-12 cuts it down to only 30 meters, making it possible to use a lower-yield warhead.
The U.S. Air Force certified its B-1 Lancer, B-2 Spirit, B-52 Stratofortress, F-16 Fighting Falcon and F-15E Strike Eagle to carry the original B61, along with the Navy F/A-18 Hornet and the since retired A-6 Intruder, A-4 Skyhawk, and F-111. The F-16s, as well as while the German and Italian Panavia Tornado, are also certified to carry the B61 for various NATO partner nations.
In 2020, the F-15E Strike Eagle became the first aircraft certified to carry the B61-12, later followed by the F-35A Lightning II and then by the B-2 Spirit, the F-16 Fighting Falcon and the German Air Force Panavia Tornado. According to NNSA, work is underway to integrate the B61-12 on the Italian Air Force’s Panavia Tornado and the U.S. Air Force’s incoming B-21 stealth bomber.
The B61-12 LEP production
Sandia said the B61-12 Last Production Unit (LPU) of the Life Extension Program (LEP) was completed on Dec. 18, 2024, although the announcement only arrived on Jan. 7, 2025. Sania then announced on Feb. 20, 2025 the conclusion of the production of the B61-12, switching to sustainment of the inventory and the production of spare components until 2026.
Earlier in 2024, the NNSA also disclosed the completion of the production of the trainers used to certify Air Force personnel and bases prior to delivery of the actual weapon systems. Trainers give Airmen the essential ability to familiarize themselves with loading the weapon on delivery platforms, as well as maintaining the weapon, said the agency. The program produced 3 different Type 3 Trainer versions with a total build of more than 100 military training weapons.
The First Production Unit (FPU) of the B61-12 was delivered in 2021, with full-rate production starting a year later. The NNSA also mentioned in earlier reports that the LEP was expected to complete production and close out in FY2026.
“Completing the B61-12 on schedule is the latest example of what we’ve been saying for several years now: NNSA is delivering capabilities at the pace and scale needed by our Department of Defense partners and our deterrence requirements,” NNSA Administrator Jill Hruby said in the announcement.
The program allows to continue to assure the safety, security, and effectiveness of the weapon, as well as consolidated and replaced the -3, -4, -7, and -10 B61 variants. “The B61-12 LEP, which is critical to sustaining the Nation’s air delivered nuclear deterrent capability, extends the service life by at least 20 years through refurbishing, reusing, or replacing all the bomb’s nuclear and non-nuclear components,” added the agency.
It is important to remember that the B61-12 is not a “new” weapon in the strict sense of the word, as it takes the warheads from the older bombs and puts them in the new body, thus leaving the same number of weapons in the nuclear stockpiles. The NNSA says there is no overall change in military characteristics of the weapon, as it balances greater accuracy provided by the modern tail kit assembly with a substantial reduction in yield.
The total program cost of the B61-12 is around $9 billion, with each warhead accordingly having a price of about $22.5 million if we consider the initial plan to manufacture 400 weapons.
