The UK SAF Mandate: Targets, Timelines and What They Mean

The UK's Sustainable Aviation Fuel Mandate took effect on 1 January 2025, making the UK one of the first major aviation markets to legally require a rising minimum share of low-carbon fuel in every litre of jet fuel supplied. For an industry that had relied largely on voluntary offtake agreements and airline sustainability pledges, the mandate marks a shift to binding regulation with financial consequences for non-compliance.

How the Mandate Works

The mandate places the obligation on aviation fuel suppliers — the companies that physically supply jet fuel into the UK market — rather than on airlines directly. Each obligated supplier must ensure that a defined percentage of the total aviation fuel it supplies each year is certified Sustainable Aviation Fuel. The obligation is expressed as a percentage of total fuel volume, giving suppliers flexibility in how they meet it: they can blend SAF into their own supply, purchase SAF from third-party producers, or trade compliance certificates with other suppliers who have exceeded their obligation.

This certificate-trading mechanism, modelled on renewable fuel obligation schemes already used in the UK's road transport sector, is designed to create a functioning market rather than forcing every individual supplier to build SAF production capacity themselves. A supplier that cannot source enough SAF can instead buy certificates from one that has a surplus, smoothing out regional and logistical bottlenecks in early years when SAF production capacity is still concentrated in a handful of facilities.

The Trajectory: 2% to 22%

The mandate's minimum SAF share starts at 2% in 2025 and rises on a defined annual trajectory. By 2030, obligated suppliers must ensure at least 10% of supplied aviation fuel is SAF. The trajectory then continues upward to a target of 22% by 2040, a level the government considers achievable given expected growth in UK and global SAF production capacity over the next decade and a half.

These are minimum obligations, not caps — suppliers are free to exceed them, and some airlines have signed offtake agreements at higher blend percentages than the mandate strictly requires, both to secure long-term price certainty and to support corporate net-zero commitments that go beyond regulatory minimums.

Buy-Out Prices and the Cost of Non-Compliance

Recognising that SAF supply will not always be available where and when suppliers need it, the mandate includes a buy-out mechanism: suppliers unable to meet their obligation through blending or certificate purchase can pay a penalty, known as the buy-out price, for each litre of shortfall. This price is set deliberately high relative to the cost of sourcing SAF, so that paying the penalty is always more expensive than actually supplying the fuel. The buy-out functions as a price ceiling and safety valve rather than a genuine compliance route — it ensures the scheme does not collapse in years of tight supply, while keeping the financial incentive firmly pointed at real SAF blending rather than penalty payments.

Revenue collected through buy-out payments is intended to be recycled back into the SAF market, supporting the mandate's broader goal of building a durable domestic production base rather than simply taxing non-compliance.

Who Is Obligated, and What It Means for the Wider Market

The mandate applies to fuel suppliers above a minimum volume threshold, capturing the major players who supply the overwhelming majority of UK aviation fuel while exempting very small suppliers for whom compliance infrastructure would be disproportionately burdensome. For airlines, the mandate does not create a direct legal obligation, but it reshapes the commercial environment: as obligated suppliers scramble to secure SAF volumes, airlines that have already locked in long-term offtake agreements with producers are better positioned than those relying on spot-market purchases.

For SAF producers, the mandate is the single most important signal in the UK market. It converts what would otherwise be a voluntary, price-sensitive market into one with guaranteed minimum demand that rises every year through 2040. That demand certainty is what allows producers and their financiers to commit capital to new production facilities with some confidence that the fuel they produce will have a buyer.

What Comes Next

The mandate's success depends on UK and global SAF production capacity scaling fast enough to meet the rising percentages without pushing buy-out payments — and therefore ticket-price pressure — too high in the interim. Industry bodies including the Sustainable Aviation coalition have argued the trajectory is achievable but will require sustained government support for production infrastructure, not just the demand-side mandate alone. The coming several years, as the obligation climbs from single digits towards the 2030 milestone of 10%, will be the period in which that becomes clear.