A trilateral programme to develop a sixth‑generation fighter with Japan, the United Kingdom and Italy has been forced off schedule after London failed to pin down its contribution. The contract that would shift the project from planning into full development — to be signed between the three governments’ co‑ordinating body and a jointly owned industrial vehicle — was due by the end of 2025 but is now unlikely before Britain settles its defence investment plan.
The partnership, known in Chinese as the Global Combat Air Programme and organised through an intergovernmental body and a joint venture (referred to in Chinese sources as “尖翼公司”), was launched in 2022 with an ambitious target of initial deployment around 2035. Signing the contract would have authorised centralised management, pooled funding and a single development timeline. Without it, Tokyo, London and Rome are expected to default to separate, national contracts with their domestic primes — a route that will complicate coordination, raise transaction costs and increase the risk of schedule slippage.
The proximate cause of the pause is domestic pressure in Britain. Under President Trump’s public push for allies to raise defence spending and with the war in Ukraine underscoring European vulnerability, the UK has embarked on an expansive rearmament programme covering new nuclear warheads, ballistic missile submarines, ammunition production and larger troop numbers. As detailed costing has progressed, the government’s projected bill has ballooned and officials concluded that even reaching NATO’s 3.5% of GDP “core” spending target by 2035 would not cover the package.
Treasury strain is acute: British officials reportedly face a £28 billion shortfall in the ten‑year defence plan and have postponed the publication of their investment priorities, initially expected in autumn 2025, until spring. That delay effectively makes it impossible for London to commit the sums needed to sign the trilateral fighter contract on the original timetable. Until funding lines are finalised, the intergovernmental organisation and the joint venture cannot be authorised to contract or to lead unified development work.
For Japan the setback is particularly awkward. Tokyo signed up to GCAP in part to secure access to advanced technologies and to keep its procurement timetable independent of US platforms such as the F‑35. A fragmented approach would leave Japan exposed to higher costs, potential gaps in capability and the prospect of buying interim solutions if the shared development drifts beyond the 2035 horizon. Italy, smaller in budgetary terms, stands to be squeezed: national suppliers could see their participation delayed or diluted.
The pause also contains a geopolitical message. Washington’s renewed pressure on European partners to spend more is reshaping how allies plan capability development. If European budgets tighten, NATO members may prioritise national rearmament and deterrence projects over costly, long‑term multinational technology programmes. That would play into the hands of US defence firms and Washington’s own strategic choices, while complicating allied attempts to field a truly non‑US sixth‑generation option.
Industrial risks multiply if centralised contracting is postponed. Multinational programmes are designed to harmonise standards, share supply chains and keep sovereign skills in play; piecemeal national contracts can fragment technical specifications, prolong testing and increase the chance that elements of the programme become incompatible or redundant. Delivering a cutting‑edge fighter requires sustained investment and political patience — commodities that appear in short supply.
The project is not dead. If London finalises its investment plan and identifies savings without gutting key programmes, the partners can still sign a contract and preserve the 2035 ambition. For now, however, the delay highlights the fragility of multilateral defence cooperation in an era of competing domestic priorities and expanding geopolitical tension. The UK’s spring budget and a renewed diplomatic push among the three capitals will determine whether the programme regains forward momentum or fractures into national efforts.