The House of Commons Library has published its research briefing on the Sustainable Aviation Fuel Bill 2024-25, the legislation that will govern how the UK mandates low-carbon fuel use across commercial aviation.

The briefing sets out the mechanics of the bill for MPs ahead of its parliamentary passage. The Commons Library, Parliament's independent research service, produces these papers to inform debate, and its analysis typically carries weight because it is non-partisan and drafted for legislators rather than industry lobbyists.

What does the bill actually change for airlines?

The Sustainable Aviation Fuel Bill is the statutory vehicle for a UK SAF mandate, the mechanism that obliges fuel suppliers to blend increasing shares of sustainable aviation fuel into jet fuel supplied to UK airports. Sustainable aviation fuel (SAF) is drop-in fuel produced from waste oils, agricultural residues or synthetic sources rather than crude oil; it works with existing engines and airport infrastructure.

For carriers, the mandate translates directly into fuel cost exposure. SAF currently trades at a multiple of conventional Jet A-1, and the obligation shifts that premium onto operators lifting fuel in the UK. For refiners and fuel suppliers, it creates a compliance market, with penalties for missing blending targets and incentives for building domestic production capacity.

What the briefing covers

The Library paper walks through the bill's provisions and the policy context behind them:

• The structure of the mandate and how obligations fall on fuel suppliers
• The compliance and penalty regime for missed targets
• The relationship between the UK scheme and equivalent mandates abroad, notably the EU's ReFuelEU Aviation regulation
• The state of domestic SAF production capacity and the supply constraints the mandate will run up against

That last point is the practical pinch. A mandate can create demand on paper, but physical production capacity determines whether airlines can actually lift the fuel. The UK currently has limited domestic SAF output, which means early compliance will rely heavily on imports until new plants reach final investment decision and construction.

Why the timing matters

The bill arrives as the UK aligns its aviation decarbonisation policy with international commitments. The UK government has set an ambition for 10% SAF in the UK jet fuel mix by 2030, part of its Jet Zero Strategy for decarbonising aviation. Legislation is the step that turns ambition into an enforceable obligation, with real financial consequences for non-compliance.

The parliamentary process itself matters here. A bill must pass both the Commons and the Lords before receiving royal assent, and amendments along the way can alter blending trajectories, penalty levels or the treatment of certain fuel pathways. Airlines and fuel suppliers will be watching for certainty on targets before committing to long-term offtake agreements with prospective SAF producers.

The verification question

As with any mandate, the gap between announcement and delivery is where the story sits. The UK's SAF ambition depends on projects that have not yet been built, using technologies — particularly power-to-liquid synthetic fuel — that remain at demonstration scale. The Commons Library briefing, by laying out the supply-side constraints alongside the legal framework, gives MPs the material to press the government on how the targets will be met in practice.

The bill's passage through Parliament over the coming months will determine whether the UK mandate begins on the government's intended timetable, and with what degree of flexibility for an industry still waiting for large-scale domestic production to materialise.