"This acquisition will provide the F-35 with an interim stand-off capability until the introduction of SPEAR 3 into service," Permanent Secretary at the MoD Jeremy Pocklington wrote in a letter to Parliament's Public Accounts Committee.
MoD authorises Foreign Military Sales purchase of SDB II (GBU-53/B StormBreaker)
The UK Ministry of Defence has approved a Foreign Military Sales procurement for the Small Diameter Bomb (SDB II), designated GBU-53/B StormBreaker in US service, as an interim stand-off weapon for the F-35. The MoD describes the munition as a roughly 200-pound (93 kg) weapon with fold-out wings that allow it to glide up to 69 miles (111 km) and a tri-mode seeker capable of radar, infrared or laser tracking.
The sale is positioned explicitly to fill a capability gap while the SPEAR 3 mini-cruise missile—intended for the F-35—awaits integration. The acquisition follows a recommendation from the Public Accounts Committee (PAC) that the MoD set out in its Defence Investment Plan (DIP) how it would maintain a stand-off capability until SPEAR 3 is fully integrated.
Lockheed Martin Block 4 delays leave SPEAR 3 unusable despite successful tests
SPEAR 3 has already passed test firings in 2024, but the F-35 cannot yet operate the missile because the Block 4 software update from Lockheed Martin—tasked with adding SPEAR 3 support—has been repeatedly delayed. The MoD now expects the Block 4 update in 2031, five years behind schedule, a timeline that drove the decision to procure SDB II as an interim measure.
The PAC's earlier report flagged the absence of a stand-off weapon as one of several essential capability shortfalls in the UK's F-35 force.
Spare parts, deployments and Operation HIGHMAST logistics shortfalls
Pocklington acknowledged shortages of spares during last year's eight-month Operation HIGHMAST deployment aboard the aircraft carrier HMS Prince of Wales. The "surge to 24 F-35B aircraft during Operation HIGHMAST exceeded the Afloat Spares Pack capacity of 12," he wrote. To mitigate the shortfall, the MoD supplemented with the Deployable Spares Pack—which is designed for land-based deployments—and took additional spares from the RAF Marham Base Spares Pack.
The Department plans to double the capacity of the Afloat Spares Pack and to procure an additional Deployable Spares Pack for land operations, but both measures are subject to approval in the Defence Investment Plan.
Engineer shortages, corrosion checks and the UK Aircraft Signature Assessment Facility
The PAC criticised the MoD for lacking suitably qualified engineers. In response, Pocklington said the number of available engineering posts will increase to 168 and that "the RAF has plans in place to fill its remaining engineering posts by 2032," a timetable driven by the MoD's estimate that it can take up to three years to make engineers fully competent on an aircraft type. He added that the number of personnel recruited into the Engineering Profession and currently in the training system has already increased.
Pocklington also warned of a likely short-term reduction in F-35 availability as the MoD steps up corrosion awareness and prevention practices—an issue the department says is particularly relevant for carrier-operated aircraft and can affect stealth characteristics. The PAC report had noted that the MoD is behind in delivering a UK Aircraft Signature Assessment Facility, needed to verify that the F-35's stealth technology remains effective and uncompromised.
What this means for the Royal Navy, the RAF, and the Public Accounts Committee
- Royal Navy: Carrier deployments that surge aircraft numbers face tangible spares shortfalls; planned doubling of Afloat Spares Pack capacity and an additional Deployable Spares Pack aim to address that but depend on DIP approvals.
- Royal Air Force (RAF): The RAF will expand engineering posts to 168 and intends to fill remaining engineering roles by 2032 as trained personnel progress through a multi-year competence pipeline.
- Public Accounts Committee (PAC): The PAC has criticised MoD procurement pacing and logistics. PAC chair Sir Geoffrey Clifton-Brown MP described the situation as "entirely unacceptable incompetence" and highlighted the risk of deploying high-end platforms without sufficient logistical support.
The chain of decisions is now clear on paper: SPEAR 3 exists and passed test firings in 2024, but Block 4 delays to 2031 mean the F-35 will rely on an American glide bomb in the interim. The stopgap—the GBU-53/B StormBreaker—provides an immediate stand-off option, but longer-term fixes for software integration, spare-parts logistics, corrosion control, and engineering capacity remain tied to the Defence Investment Plan, which has no current publication date despite being due in autumn 2025. Until that plan is published and funded, the UK's declared interim measures will have to suffice for both operational commanders and the PAC's scrutiny.
Original story: https://www.theregister.com/security/2026/05/18/f-35-software-delays-leave-uk-buying-time-with-us-glide-bombs/5241737
