The UK’s F-35B Lightning II programme is entering a pivotal phase, as the Ministry of Defence prepares to declare Full Operating Capability (FOC) by the end of 2025.

In a recent letter to Parliament, Defence Minister Maria Eagle provided a detailed update to the Defence Select Committee, highlighting delivery progress, future upgrades, and the aircraft’s expanding operational role.

“The declaration of Full Operating Capability for the first procurement phase is scheduled to occur no later than 31 December 2025,” wrote Eagle, adding that “graduation as a Government Major Projects Portfolio programme” is expected by March 2026.

So far, 36 out of 48 aircraft have been delivered under the first procurement phase, with the remaining jets due for delivery this year. According to Eagle, the programme remains on schedule, despite production delays caused by software instability linked to Lockheed Martin’s planned Block 4 upgrade.

“I would like to assure you and the Committee that the delivery plan will not impact the scheduled Full Operating Capability declaration,” she said, noting that further UK deliveries are expected in May.

The Minister confirmed that the UK still intends to grow its fleet to 74 aircraft and stand up a third frontline squadron by 2033, subject to the outcome of the ongoing Strategic Defence Review. Funding for this expansion has already been allocated.

As for the long-anticipated Block 4 capability upgrades, Eagle explained that a formal “sub-programme of capability enhancements is being established, with Congressional oversight, to deliver by 2033.” This suite of upgrades aims to “improve the survivability and lethality of the aircraft,” with UK-specific weapons such as the METEOR beyond-visual-range missile and the SPEAR 3 precision strike weapon under consideration.

Operationally, the F-35 fleet has grown in versatility. In 2024, British F-35s took part in NATO Air Policing from Iceland, and shortly after, embarked on maritime operations from HMS Prince of Wales. Eagle described this transition as evidence of the force’s flexibility: “The Lightning Air Wing pivoted within a month to maritime operations, to again work with NATO from HMS Prince of Wales.”

The UK’s newest frontline squadron, 809 Naval Air Squadron (NAS), was recommissioned in December 2023 and is continuing its work-up throughout 2025. Later this year, 809 NAS and 617 Squadron (‘The Dambusters’) will jointly deploy aboard HMS Prince of Wales as part of Operation HIGHMAST—marking the first time two UK F-35 squadrons embark together.

“This operation will display our global Carrier Strike reach,” said Eagle, describing it as a demonstration of Britain’s ability to “deploy, operate and command a Carrier Strike Group consisting of two UK Lightning squadrons, with associated support.”

The carrier strike group will travel through the Mediterranean, Middle East, and into the Indo-Pacific, working closely with allies including Australia and Japan. It is expected to highlight UK commitment to international maritime law and freedom of navigation in increasingly contested waters.

In closing, Eagle reaffirmed the long-term importance of the platform, stating: “This has been a very positive period for F-35 Lightning… it will remain at the forefront of our military for decades to come.”

George Allison
George has a degree in Cyber Security from Glasgow Caledonian University and has a keen interest in naval and cyber security matters and has appeared on national radio and television to discuss current events. George is on Twitter at @geoallison

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  1. The good bit is that we are going to get a bumper buy of 13 F-35s this year (though other reports say by end 2026).

    The bad news is that Block 4.is not now going to be ready until 2033, another 3-4 years slippage. It really is a bit of a fiasco by LM.

    More worrying still is her line that ‘Meteor and Spear are ‘under consideration’ in that 2033 target date. Under consideration??? I thought they were a key element of Block 4 for us? It’s almost as if someone really wants us to buy US missiles, rather than our superior UK/European ones.

    • This programme is a turd, I hope its the last time we buy US. We have wonderful world leading tech aircraft, whoopppy doo awesome. They are armed with last century’s weapons, ahhhhhh….

        • Such as?
          Serious question as I have heard French people complain that their government is so obsessed with exports their troops get cheap so-so stuff that sells.

          • The French could teach us a thing or two when it comes to equipping the Army.
            A full range of vehicles, in a sound plan they’ve stuck to.

          • They have an army that is fully equipped with a good selection of modern armoured fighting vehicles.. their armoured infantry have cannon armed IFV, their mec infantry have modern APCs 25ton range APC, their version of light role infantry all get decent 10-15 ton range protected protected mobility vehicle even their air mobile formations get a decent 4 wheeled protected mobility vehicle… they have a modern armoured cav vehicle armed with a cannon and Anti tank missiles, they will get 3 regiments worth of modern MBTs..

            All in all they are getting for 2030 around 5000 modern armoured vehicles for the British armies 600 boxers, 150 MBTs and 500 ajex versions.

        • If QE/PoW were STOBAR, then one sqn of FAA Rafale M, able to buddy refuel F-35B would be handy. The Rafale could also carry ASN4G to give the UK a tactical deterrent again.

          • As a French l was thinking the same.And l wonder if we could modify our Mistral LHD to receive British F35Bs.It would be could for our interoperability.

    • LM has to refocus very fast, including speeding up foreign weapons integration; F-47 may kill further US F35A orders. The 6th-gen naval program along with the USN’s re-assessment of their high/low mix is not good news for the F35c.

      Then there’s Canada (potential split fleet), Germany (French/UK replacement of US tac nukes), Portugal (removing it from the running), others reassessing final numbers etc. etc.

      F35b is about the safest of the variants this second and it needs UK weapons on it.

    • Yes I picked up in the spear 3 and meteor under consideration bit. That’s a worry because the MAGA and defence lobby will work to cut out a competitors products if they can and I suspect we have no leverage to prevent. You have to wonder if spear 3 and meteor will ever get past the finish line of integration.

      • Just a thought, but is it possible for the 3 US based orange wired aircraft to be brought back to the UK to carry out integration trials, or am I missing some of the wider picture.?

        • We don’t have access to the source code which is required..essentially we codeveloped to aircraft and stitched us by refusing to hand over the source code..then the rubbed salt in by giving it to Israel a country that had not contributed anything to the development.

    • It’s worth noting block IV doesn’t really exist now it’s been split up so it’s likely much of the anticipated capability will be delivered before 2033.

    • Sadly true, at the rate Block 4 is ready to come into service, it is about the same time Tempest is supposed to be at IOC. Not a great situation to be in, especially if things kick off. As we will have to buy weapons that are already cleared for the aircraft, to give it some stand-off capabilities. The alternative is do what Ukraine and Turkey have done. By integration a touchscreen tablet into the cockpit and using that as a pseudo stores computer. Where weapons can be integrated much easier.

  2. I would really appreciate it if there was some clarity provided on what Block IV capabilities will be made available when, between now and 2033- but I suppose that’s too much to ask of the JPO or our government.
    I can only hope that we went out to bat and told them there’ll be no more aircraft ordered until Meteor and Spear 3 are slotted into the integration schedule between now and 2027. But I realise that hope would be classified as forlorn.

  3. It seems obvious thus is deliberately being done to force sales of US weaponry rather than alternates.

    • There is not much if any US weaponry going on it either though.

      Never attribute anything to malice that can be attributed to incompetence 😀

      Storm Breaker which is a poor man’s SPEAR 3 is in testing but no announcement of when it will be ready for F35 deployment so likely 2027 atleast.

      AIM 260 is the US closest equivalent to Meteor and it still is not even in testing for F35

      JSM and LRASM seem to be the only major capability added in the last few years but I don’t think anyone is complaining about getting some much needed anti ship capability and JSM was part of the Norwegian and Australian integration originally although the US later adopted it.

      • Yes, pretty much. Sidewinder, AMMRAM, various smart bombs, and the JSOW have already been integrated into the F-35. but as you state, Stormbreaker and LRASM/JASSM are the current US weapons undergoing integration and they aren’t setting any speed records either.

        Stormbreaker is supposed to EOC soon, on USMC F-35Bs first. Other than software integration though, there are hardware considerations. The bomb racks need to be ordered as well, the USN/USMC is using the BRU-61 four-spot bomb rack for Stormbreaker in their F-35Bs and Cs (Super Hornets use the 2-spot BRU-55 rack). Significant orders of BRU-61 racks won’t hit the USN inventory till next year.

        I don’t know what bomb racks Britain is using for SPEAR 3, but they could be a further reason for integration delays.

        As you said, the USAF has ordered JSM for their F-35As, but I don’t follow the Air force much and I don’t know of a timeline for JSM integration. If the USAF is also eagerly awaiting JSM integration even though they are waiting on JASSM/LRASSN already, I don’t think delays can be attributed to conspiracies within the US MIC. Everyone is waiting, even the US.

    • Coupled with the Tangerine Toddler Tantrums it may well result in no new platform sales at all!

      Who wants to be held hostage to people like Trump and Vance? They don’t come across as either obligate or easy to work/negotiate with.

  4. There is video of Meteor doing drop testing from an F-35 on the ground, and there are still photos of Meteor doing flight testing in a weapon bay an F-35B, so there is visible evidence that Meteor integration is happening on F-35.

    Lots of angry talk about SPEAR 3 here, but isn’t it still in the testing phase, even on Typhoon? If it’s not operational on any platform yet, it makes sense that integration of SPEAR 3 will take longer on the F-35. LM needs to hurry up, but slow SPEAR 3/F-35 integration seems to be at least in part due to factors outside of the F-35 program.

    • Integration of Meteor and other Weapons Systems to my untrained mind will take Two Stages – firstly Carrying/Drop Trials,where the Weapon is tested physically for carrage and release,then secondly all the Software Coding and Computer side of it.Meteor has had a redesign for it to fit in the F35b Weapons Bay,maybe this has been done,as what you describe,but LM can only do the Software side which is causing the delay.

      • It sounds pretty complicated and time consuming. Modifying a missile is time consuming by itself. It has to be frustrating for the different countries involved, but Meteor integration is actually happening, if slowly.

        UKDJ did a piece on Meteor integration (with the flight test photo I mentioned) on 28 Feb, 2025 if you haven’t seen it. I saw the drop pit test video on X, (Doha104p3). Its a short series of several different weapons including Stormbreaker and Meteor being dropped from a parked F-35 into a foam padded pit, seemingly so prove that nothing gets caught on the door-mounted AMMRAM on the way down.

    • Typhoon integration is a relatively new development, it was previously only meant for F-3 up until a year or so ago.
      It’s a bit unclear as to the reasons for the delay on Spear 3, but it could easily be as much about slow F-35 development as the weapon itself.

    • Think I’ve been harsh on Lockheed Martin I have just googled spear 3 has been typhoon test bedded but presently no indication that spear 3 will by available to typhoon by uk govt, so we can moan but righteously.

  5. The Superb F35(B) continuing to prove the sceptics wrong again, I’m confident this excellent aircraft will go down in history as one of the all time greats.

  6. It wouldn’t surprise me if the Trump adminstration were behind the ‘delay’ in Block 4. Can anyone see us retro-fitting a separate targetting system and wing pylons for Meteor and Spear 3? It would make a dogs dinner of the stealth envelope and would be a real Heath-Robinson …. but it might just be a way of bringing a wider weapons set into the F35B inventory. Absolute shocker this is now delayed till 2033. I wouldn’t buy beyond the 48 until this is sorted. This isn’t value for money.

      • It’s, what? £10M cheaper than the 4.5 Gen alternative we use (Typhoon)? Of course, it offers a far more capable ISR capability with its sensor suite and offers VSTOL-to-Mach 1.x capability, for which there is no alternative, but when it can only use what seems to be widely recognised on here as a less capable suite of weaponry, with a road map to Meteor and Spear3 that continues to be kicked down the road, it’s hardly offering what was presumably billed when the MOD signed a contract for them. So, value for money? No, I’m not convinced.

        • Simple sales volume means that the huge development costs can be spread over more airframes.
          Typhoons = 609 delivered
          F35 = 1,110 delivered with hundreds ordered

        • Cheaper acquisition cost but more expensive maintenance cost, therefore overall higher operational life cost than Typhoon.

          On problem of Trump and USA unreliability as an ally in the future, it might behove the UK to convert one of the carriers into a CATOBAR vessel and operate the French Rafale from it while limiting F35B lifetime purchases to no more airframes, except attrition replacements, for the remaining STOBAR carrier.

          If Tempest can’t be navalized for a reasonable price, then the UK can wait and acquire whatever aircraft France develops for its PANG carrier to replace the Rafale or in the worst case scenario and France does not produce a 6th gen aircraft for PANG, the converted UK CATOBAR carrier can be equipped with the F35C variant when a sane government returns to Washington. The F/A XX may be too rich for HM treasury.

          • As a French I fully agree with you, but Rafale doesn’t need CATOBAR, STOBAR is enough and would be less expensive.The French could also maybe modify their Mistral class LHDs to receive F35Bs that would be good to enhance our operability.Unfortunately our politicians made the mistake to have only one carrier.

    • About 16 years behind schedule.

      Perhaps time to talk to Boeing about buying f32b airframe IP and integrating with Tempest sensors / architecture

    • You’re crediting the MAGA-bozos with way more cunning than they actually have. The Signal debacle shows them to be incompetent idiots completely out of their depths.

    • There is no conspiracy theory that connects US Politicians to the delays in the F35 Programme,quite the opposite in fact.They have been on LM’s case for years holding them to account ,and trying to get them to deliver on what they promise.Multiple times they have threatened to cancel the whole project.

    • No, full delivery of what used to be Block 4 by then.
      They could just as easily be in the first delivery of what was Block 4 but is now split into lots of seperate upgrades.

      • ‘Could’ being the operative word there.
        The only thing we know right now is that we’ll have it by 2033, at least until the next announcement from LM.

  7. I’m starting to think the F-35 was just a Silicon Valley style industry disruptor. Designed during ‘the end of history’ to eat NATO’s fighter budget and starve off European competition, not to actually deliver functional fighters.

    • like the rubbish starfighter at the beginning of the cold war sold to western europe. it just makes tempest all the more important to ensure aerospace industry other than in usa

    • getting dark now but in years to come it maybe revealed LM were taking money from american firms to slow block 4 . i have no facts to back that statement

      • Looks that way, I would be surprised if European weapon integration wasn’t the absolute last item on the list.

  8. Well my wishlist for UK F-35 includes Israeli levels of digital autonomy, a big UK spare parts stockpile, Meteor, Spear3 & JSM fully integrated. I would not make any large buys of F-35 until sanity returns to the White House & F-35 gets APG85, ECU, stealth drop tanks, new EO & cooling.

  9. I’m hoping SDSR adds a final batch of upto 36 more F35Bs delivering 80+ airframes into active service and then we pause contribution to the programme and go all in on Tempest/ GCAP
    Also wishing the RAF will get some new typhoons to see them through to Tempest.
    We shall see what happens. One thing is for sure SDSR 2025 is going to prove a very interesting read.
    Interesting article in the press today (think it was the telegraph which I rarely read) comparing the UK and Norway facing the threat of Russia’s northern fleet. In essence calling for more Poseidon MPAs, additional type 26 specialist ASW frigates and GBAD capable of protecting the UK
    The threat posed by Russia is from upto 800 cruise and hypersonic missiles the Russians could in theory fire at us. Admittedly most of those wouldn’t be accurate but the potential for a saturation conventional explosives armed attack to knock the UK out of a conflict on day one is a real concern.

    • Russia’s northern fleet has 25 nuclear powered subs and 4 diesel electrics.
      UK and Norway. 6-7 active SSNs and just 4 conventionally powered SSKs. Even pulling in French SSNs our European nuclear attack fleet in theory is outnumbered 2:1 without USN support. We need more subs too. Got to get back upto 12-15 SSNs again.
      A batch 2 Astute would be a wise idea and keep the yards ticking over until SSNr/ Aukus comes along and is probably the best option to uplift SSN numbers.

  10. The Times is claiming that we’re going to purchase F35A aircraft to replace T1 Typhoons. I can only assume that these will be in addition to the carrier variant.

  11. This is why Typhoon is so important to the UK, F-35B is great but will be amazing with stand-off weapons like Meteor, Spear-3 and JSM, if they ever obtain that capability.
    Typhoon has more options already and we have access to software to add more.
    Personally think the F-35B fleet needs to be mid 80’s to be effective but also think that we need Typhhon to compliment it. The Typhoon fleet will shrink with time/airframe life prior to Tempest so we need 25 more to keep the fleet at a sensible level through until Tempest and provide the UK with a realistic offensive threat.
    F-35A would be a mistake and would undermine any future Tempest purchase.
    We could really make carrier strike impressive with a deployment of two Sqns of F-35B with Metor, Spear-3, JSM, along with a drone AEW system and air to air refuelling by Drone.
    If we are going for drones through project Ark Royal, let’s ensure they will take the weight of at least Rafale to allow STOBAR or CATOBAR cross decking, it seems daft to add EMALS that won’t take manned jets.
    If heavy drones are not an option due to cost of carrier conversion and system development, then we need to look at vertical lift through Cv-22 or similar to provide an AEW, refuelling option.
    We could have a really impressive carrier system, best look down the back of the sofa for some spare cash !!

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