The United Kingdom has taken delivery of the last F-35B from its initial 48-aircraft order, completing the first phase of its participation in the Lockheed Martin-led stealth fighter program.
The final jet was accepted on March 27, according to the Defence Equipment & Support (DE&S) procurement agency. The milestone brings total deliveries to 48 aircraft, although the active fleet stands at 47 after one jet was lost in a 2021 accident aboard the aircraft carrier HMS Queen Elizabeth.
The UK’s F-35Bs are jointly operated by the Royal Air Force and Royal Navy from RAF Marham in eastern England, forming the backbone of the country’s carrier strike capability.
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The latest aircraft delivered are built to the Technical Refresh 3 (TR-3) standard, which introduces upgraded hardware designed to enable future Block 4 capabilities. However, the associated software package has yet to be fully cleared for combat use, limiting these jets to training and non-operational roles for now.
The completion of the first batch comes amid continued uncertainty over the next phase of the program. The UK government has yet to publish its Defense Investment Plan, a long-delayed 10-year spending and procurement roadmap that is expected to define future F-35 orders.
Britain has a stated requirement for up to 138 F-35s as a Tier 1 partner in the program, but funding and timelines for additional aircraft remain unresolved. The delay has created planning challenges for both the armed forces and industry, with no firm contract in place for the next tranche.
A shift in fleet composition is already planned. Under the Strategic Defense Review released in June 2025, the UK intends to acquire 12 F-35A conventional takeoff and landing variants for the RAF, reintroducing a nuclear delivery role within NATO. This decision reduces the expected second batch of F-35Bs from 27 to 15 aircraft.
Despite procurement uncertainties, the UK’s F-35 force has been active operationally. Eight aircraft from 617 Squadron are currently deployed to RAF Akrotiri in Cyprus, where they have flown defensive missions across the Middle East following the escalation of conflict involving the United States, Israel and Iran.
Those operations have included the first combat use of British F-35s in air-to-air engagements, with RAF pilots intercepting one-way attack drones during missions over the region.
The longer-term trajectory of the program will depend on when the UK government finalizes its defense spending strategy, which is expected to determine how quickly — and in what configuration — the fleet expands beyond its current size.
