To mitigate delays in the integration of the SPEAR 3 missile, the Ministry of Defense confirmed that plans to acquire SDB II ammunition from the US through a Foreign Military Sales (FMS) program have been given the green light.
First reported by our friends at the UK Defense Journalto letter published on May 14, 2026dated 30 April 2026, from the Permanent Secretary of the Ministry of Defense to the UK Public Accounts Committee (PAC) states that “approvals have been granted to proceed with a Foreign Military Sales (FMS) procurement of the precision guided munition, Small Diameter Bomb (SDB-II). This procurement will provide the F-35 with an interim standoff capability until the introduction of SPEAR-3 into service.”
The Ministry of Defense has approved the acquisition of the Small Diameter Bomb II as a provisional confrontation weapon for the F-35. Click on the image for more information.https://t.co/48Tp6dXPoW
— UK Defense Journal (@UKDefJournal) May 14, 2026
The statement was made in response to the PAC’s earlier recommendation that the MoD “should set out in the Defense Investment Plan how it will ensure a stand-off capability in the coming years before the Spear 3 is fully integrated into the aircraft”. He National Audit Office (NAO) had previously reported that while plans to acquire SDB II had been discussed, funding had not yet been approved.
While we are still waiting for the plenary session, Defense Investment Plan (DIP) very delayed to be published, the acquisition of SDB It has already been practically confirmed be part of the plan.
🇺🇸🇬🇧 The UK National Audit Office recommended, and (according to Aviation Week) the next Defense Investment Plan will fund the acquisition of the GBU-53/B StormBreaker (Small Diameter Bomb II) for this reason.
Spear 3 is very comparable to SDB II, while SDB I would provide… https://t.co/azt0cO5Ttq pic.twitter.com/8TuYVT2DHp
– Colby Badhwar (@ColbyBadhwar) December 11, 2025
As The aviationist and many others have previously reported, the UK’s F-35 Lightning II fleet is very poorly equipped with air-to-surface weaponry. Despite the large number of options available for the aircraft elsewhere, in UK service the aircraft currently rely solely on the Paveway IV precision guided bomb. While the Paveway IV is well regarded for its excellent performance, as an unpowered bomb without a glide kit it is largely a substitute weapon and is riskier to use in contested airspace.
Meanwhile, the GBU-53/B StormBreaker, or SDB II, uses deployable wings to extend its endurance beyond 100 kilometers under ideal circumstances. While it has a shorter range than the turbojet-powered SPEAR 3, it provides a valuable interim capability that may in fact be retained even once SPEAR 3 enters service.
GBU-53/B #stormbreaker Air turbine pop-up alternator. pic.twitter.com/Vpqdy5i7X2
— Air power | MIL-STD (@AirPowerNEW1) March 10, 2025
Like SPEAR 3, each F-35B can carry eight SDB IIs internally at the same time: four munitions in each internal bay. This exceeds the total payload of the Paveway IVs carried even in the “beast mode” configuration, which includes four bombs carried externally on the wings and two internally. This means that the SDB II could become the weapon of choice even in some situations where maximum stealth is not required, allowing a single aircraft to attack more targets during each sortie (and, if all weapons are carried internally, also making the aircraft more aerodynamic and fuel efficient).
#F35 BF-5 double GBU-53/B SDB-II #stormbreaker release. April 2023. NAS Patuxent River. Currently integrated into all variants of the F-35, the StormBreaker is an all-weather precision guided munition capable of operating in GPS degraded or denied environments. Your tri-mode search engine… pic.twitter.com/RCLkCWcRrJ
— Air power | MIL-STD (@AirPowerNEW1) February 21, 2026
F-35 spare parts status
The Permanent Secretary’s letter also reveals that when F-35Bs were deployed aboard HMS Prince of Wales during Operation Highmast, also known as Carrier Strike Group 25, the number of spare parts available was below the ideally desired level. Even though 24 F-35Bs were deployed aboard the ship (an increased force intended to meet the requirements for declaring full operational capability), the spares package on board remained at a level normally designed for 12 aircraft.
Spare parts packages are standardized sets of spare parts designed to support the routine operation of an aircraft away from its base. For the UK’s F-35B force there are Deployable Spare Parts Packages (DSP) designed for land deployments and Afloat Spare Parts Packages (ASP) for aboard aircraft carriers. To mitigate the reduction in spares numbers, additional materials were withdrawn from DSPs and RAF Marham to supplement the carrier’s stockpile. However, the nature of a carrier’s deployment and the difficulties in maintaining a supply chain to the ship created problems in ensuring these were delivered on time.
There are plans to double the capacity of the ASP and acquire an additional DSP. These are expected to be confirmed in the Defense Investment Plan (DIP).
The letter reveals issues with corrosion and confirms Aviation Week’s earlier report that the UK will purchase the Small Diameter Bomb (SDB-II) to give the UK’s F-35Bs something resembling an air-to-ground separation capability. And the less is said about #marhambetter. https://t.co/Ic4m5AVMni
– Tony Osborne (@Rotorfocus) May 14, 2026
The Secretary says that lessons have been learned following these difficulties, and new planning processes have now been put in place, already in place for the deployment of F-35B aircraft to RAF Akrotiri.
Mission Capability (MC) rates for the F-35Bs in Operation Highmast were comparable to the global average for the variant, exceeding the average by some points. Since the end of the long deployment, rates have declined as the F-35B force regenerates and the aircraft rotate through corrosion repair programs.
