The Ministry of Defence says assessments of UK F-35 availability need fuller context and argues that the standard availability metric used across the global F-35 programme does not reflect how the fleet is actually operated.
Ben Obese-Jecty MP asked why UK availability between October 2024 and January 2025 amounted to only around two-fifths of the availability level recorded by the global F-35B fleet, citing paragraph 11 of the Public Accounts Committee’s report The UK’s F-35 stealth fighter capability.
Correction 18/11/2025 – An earlier version of this article stated that the Ministry of Defence “disputed NAO F-35 availability figures” and referred to the availability calculation as “the NAO method”. In fact, the MoD was challenging the way those availability figures were used to represent UK “capability usage”, rather than disputing the figures themselves. The metric in question is the standard availability measure used across the global F-35 programme, with data collated by the Joint Program Office in Washington DC. The article has been updated to reflect this.
Responding, Defence Minister Luke Pollard said the MoD will not publish availability figures for 2023, 2024 or 2025 for what he described as operational security reasons. He also noted that the National Audit Office had redacted its own numerical availability data for the same reason.
In its findings, the NAO concluded:
“The MoD is delivering F-35 availability far below its targets. In 2024 the UK F-35 fleet achieved approximately half of the MoD’s target for mission capable rate… The UK F-35 fleet achieved approximately one third of the MoD’s target for full mission capable rate. UK availability rates also compared unfavourably with the global F-35B fleet… approximately three-fifths that of the global fleet for mission capable rate and approximately two-fifths for full mission capable rate.”
The NAO stressed that this availability metric is the standard measure used by all F-35 partner nations, with data collated by the Joint Programme Office in Washington.
Pollard argued that relying on the 24-hour availability metric to judge “capability usage” does not align with how Combat Air forces are generated or employed. He said the late-2024 and early-2025 data reflected a routine force-generation period that included regeneration after a carrier exercise, scheduled aircraft maintenance, and seasonal leave across both squadrons.
The Public Accounts Committee offered a sharper assessment. It described F-35 availability as “poor” and “significantly below” UK targets, reporting that the fleet met “approximately one-third” of the MoD’s full-mission-capable target during 2024. The committee said UK availability in the October 2024 to January 2025 window was “two-fifths of the level of availability of the global F-35B fleet”.
The PAC flagged enduring shortages of engineers, instructors, cyber specialists and pilots, as well as capability gaps including the absence of a standoff weapon until Spear 3 arrives in the early 2030s. It has asked the MoD to set out how it intends to raise availability and sustain capability after Full Operating Capability is declared.
Hang on chaps, I’m just pulling up the comfy chair, got a few logs for the fire and a fresh brew on, be ready in a minute.
Right, go for it !
I’m thinking It’ll get Political early on with a few “Drive by’s” a bit later, then a whole bunch of epic essays and some brand new names in the early (hic) hours. 🤡
Steady with the caffeine at this time, you’ll not sleep
If the NAO methodology is wrong why didn’t the MoD challenge it in the report.
How can they underperform other F35B fleets if it’s simply a question of the wrong measurement.
So the NAO and the MOD are disputing the claimed figures, but both parties are redacting the only basis on which their claims could be judged, on security grounds?
You can’t say that the figures are wrong, but for security reasons you won’t reveal the right ones. If you really believe the figures are a national secret, you just need to shut the hell up and let the chips fall where they may. As it stands, nobody believes the figures are a secret (the US publish theirs and we even publish our targets). This sort of nonsense leaves MOD in the worst possible position.
Does anybody believe a word these Charlatans say anyway?
I don’t.
However, big effort with CSG 25 so BZ for that.
It has reached super farce levels now.
Trying to hide the effects of decreasing spend and cuts this way is beyond a Sir Humphrey Appleby joke.
I would hazard a guess and say they (the MOD) are working on the principle that if the planes don’t actually fly they won’t break or suffer wear and tear. This way they will technically stay active for longer.
You might well jest but, I am a firm believer in using vehicles as they were intended. Motorbikes are good examples of this, they are way better to ride when used and maintained constantly and the engines perform better when thoroughly revved. Having a Bike sat around in the garage waiting for nice weather does them no good at all. Even White Van Man knows that a high mileage Transit that has been Thrashed, performs way better than one that just gets driven around town.
With so few F35’s I find It difficult to understand how we can be so bad.
I recall that in spring 2024 the MoD revealed availability figures for CR2 tanks in answer to a written question from an MP; the figures were on par at 70%.
Why the coyness about what MoD considers to be true ‘adjusted’ figures for F-35B? Presumably the figure is terrible.
Open source press estimates for mission capable availability (at least one primary mission capability) are around 30%. I’ve found no open source estimates for fully mission capable, but looking at the US figures they’ll be somewhere below 10%. New deliveries have the highest availability and that degrades over the first few years as lack of spares and engineers makes it impossible to keep them in tip-top shape.