The Rhodium Group has published an analysis asking one of the most consequential questions now facing air transport: how quickly can sustainable aviation fuel scale?

The question is not academic. Airlines across the United States, Europe and Asia have signed SAF offtake agreements covering volumes that exceed current global production capacity several times over. Regulators on both sides of the Atlantic have written SAF mandates into law, and aircraft manufacturers have designed their current product lines — from the Airbus A320neo family to the Boeing 787 — to fly on blended SAF today and on 100% SAF in the future.

The supply side has not kept up.

Rhodium's analysis, titled "Seeking Alternatives: How Fast Can Sustainable Aviation Fuel Scale?", examines the pace at which SAF output can expand. The report situates the question within a broader policy and investment debate: aviation accounts for a small but stubborn share of global carbon emissions, and unlike ground transport, the sector has no near-term path to electrification for long-haul operations. Liquid hydrocarbon fuel — drop-in or blended — remains the only practical energy carrier for the aircraft now flying and those in the backlog.

That reality places the burden of decarbonization on fuel production. It also places a cost burden on carriers. SAF currently trades at a substantial premium to conventional Jet A, a premium that flows directly into airline fuel bills — the largest or second-largest operating expense for most carriers. How fast that premium narrows depends on how fast production scales, which in turn depends on feedstock availability, refinery conversion capacity, capital deployment and policy support.

These are the variables Rhodium sets out to interrogate.

For the airline industry, the stakes are measurable in fleet and network terms. Carriers in Europe face ascending SAF blending obligations under the ReFuelEU Aviation regulation, which requires suppliers to increase the SAF share at EU airports in staged steps over the coming decades. Singapore, Japan and other Asian governments have set their own targets. United States policy has shifted with each administration, complicating long-term offtake economics for domestic producers.

Each of those mandates converts a voluntary corporate sustainability pledge into a compliance cost with a compliance date.

The scaling question also divides the industry along technical lines. SAF produced via the hydroprocessed esters and fatty acids pathway — HEFA — dominates current output and draws on finite waste oils and fats. Alcohol-to-jet and power-to-liquids pathways promise larger eventual volumes from more abundant inputs, but both remain earlier in the cost curve, with fewer commercial-scale plants operating. Analysts disagree on when, or whether, those pathways close the price gap with conventional fuel without subsidy.

Rhodium's contribution to that debate matters because its analysts have tracked energy transition economics across sectors, and aviation fuel scaling sits at the intersection of agricultural policy, refining capital cycles and climate regulation. If SAF output grows slower than mandate schedules assume, the result is either higher pass-through costs to passengers, delayed compliance, or both. If it grows faster than expected, early offtake signers lock in advantage.

For fleet planners, fuel buyers and lessors pricing residual risk on aircraft financed over 12-year terms, the answer to Rhodium's question is not background noise. It is a direct input into the operating-cost assumptions that underpin aircraft valuations and network decisions.

Rhodium's analysis suggests the industry should watch announced production capacity against actual plant commissioning dates — the same discipline applied to aircraft delivery schedules. Promised volumes, like promised deliveries, do not fly until they do.