In 2025, SAFs represent approximately 0.7% of global fuel consumption for airlines according to IATA. The Shift Project, in its February 2026 report, diagnoses the situation in figures: according to the Shift Project, alternative fuels could cover a growing share of the sector’s needs by 2050, but this trajectory requires massive investments and unprecedented land and energy trade-offs. Yet the industry is planning, over the same period, to double traffic. The gap between these two trajectories defines one of the most difficult trade-offs in the energy transition.
The Essentials
- Aviation cannot be decarbonized through technology substitution alone: the Shift Project does not put the maximum SAF share at 50% by 2050 in the consulted report.
- The report presents a decline of at least 15% in traffic over five years for a budget compatible with +1.7 °C; the industry projects exactly the opposite, a doubling by 2050.
- The constraint is as physical as it is economic: electrolysis capacity and available agricultural land limit SAF production, independent of political intentions.
- Three trajectories exist: organized sobriety, technological bet, or regulatory fragmentation between geographic zones. None is without cost.
- A reinforced carbon price signal and a multilateral agreement aimed at reconciling traffic growth with climate constraints remain insufficiently mobilized levers.
0.1%: The Gap Between Ambition and Actual Production
The figure deserves repetition. In 2025, SAFs represent approximately seven thousandths, or 0.7%, according to IATA. Airlines, manufacturers, and governments have been talking about SAF for ten years. Actual production is there.
The Shift Project report “Flying Without Oil” documents why this gap exists. SAFs divide into two main families. Bio-SAF is produced from biomass: animal fats, agricultural residues, dedicated crops. E-SAF is synthesized by water electrolysis to produce hydrogen, then combined with captured CO₂. The report specifies that the technological bet assumes a ramp-up of e-SAFs, but does not demonstrate that liquid hydrogen will be operationally available at large scale before 2040.
Both sectors have hard physical constraints.
For bioSAF, limits concern available sustainable biomass, land area, climate, and competing uses. Mobilizable land without encroaching on food production or forests is limited. Scaling up bioSAF production requires land trade-offs that few countries are ready to make explicitly. For e-SAF, the constraint is low-carbon electricity. Producing one liter of e-SAF requires significantly more electricity than a vehicle consumes to travel an equivalent distance.
At the scale of the global fleet, required electricity quantities are considerable and create allocation tensions with other decarbonization needs.
The May 2026 note “Electrifying Our Industry: The Path to Autonomy” is attributed by the Montaigne Institute to Joseph Dellatte. E-SAF for aviation shares electrolysis resources with other priority industrial sectors. The financing and deployment of electrolyzers constitute a collective trade-off that neither the market alone nor statements of intent can resolve.
The electricity grid itself illustrates this tension: the race for investment in electricity transmission infrastructure is already under pressure before industrial demand for electrolysis even ramps up.
The Industry Plans for Doubling, Physics Says Otherwise
ICAO projections imply approximately 7.8 billion additional annual passengers between 2024 and 2050. Growth is driven by Southeast Asia, India, sub-Saharan Africa: markets where the middle class is accessing air travel for the first time. This dynamic is real and legitimate. It does not change physical constraints.
If traffic doubles and SAFs cover at most half of energy needs, the sector will consume in 2050 roughly as much fossil kerosene as today, in the best case. Aviation today accounts for approximately 2.5% of global CO₂ emissions, but its real climate impact is higher because contrails and high-altitude emissions have an additional warming effect. Maintaining this footprint in absolute value in a world seeking to reach carbon neutrality raises a compatibility question with the most ambitious climate targets.
The Shift Project report identifies a decline of at least 15% in traffic over five years as necessary for a scenario compatible with +1.7 °C. This recommendation contradicts short-term growth projected by the sector, without being its exact opposite over the entire period until 2050. The gap is not marginal. It is structural.
The European ReFuelEU directive, adopted in 2023, imposes increasing thresholds for SAF in fuels sold in Europe: 2% in 2025, 6% in 2030, 70% in 2050. These obligations exist. But their overall impact depends on what happens outside Europe, and nothing in the directive constrains total traffic volume.
Three Trajectories, Three Different Bets
Facing this gap, three trajectories are emerging. They do not entirely exclude each other, but they rest on very different political and economic bets.
The first is organized sobriety. It involves capping, then reducing air traffic by starting with short flights and routes replaceable by rail. An emissions quota per passenger, a significant carbon price signal integrated into the ticket, a reorientation of public subsidies toward long-distance rail: these tools exist. Several European countries have already banned certain short domestic flights. France banned in 2023 flights of less than two and a half hours of rail travel time on routes covered by train.
Austria did the same. These measures remain marginal in volume.
The second trajectory is the technological bet. It involves maintaining traffic and betting that SAFs, an increasing share of which would be e-fuels, will be available at large scale, while liquid hydrogen remains in development phase for medium-haul routes. Airbus is developing hydrogen planes for medium-haul routes. The technology is real. But certification timelines, fleet renewal, and infrastructure deployment stretch over several decades.
An aircraft put into service in 2035 is still flying in 2060. Betting on a breakthrough technology operational before 2040 amounts to assuming that virtually all production, cost, and infrastructure obstacles will be lifted in fifteen years, when in 2025, approximately 0.7% of airlines’ fuel needs are covered by SAFs according to IATA.
The third trajectory is regulatory fragmentation. The European Union imposes constraints, while Asian states are not subject to ReFuelEU outside the EU. The surcharge related to SAF affects operations in the ReFuelEU scope, regardless of the airline’s nationality, but regulatory asymmetries territorialize competitive advantages. Traffic shifts to less constrained hubs. Global emissions stagnate while European competitiveness declines.
This is a scenario that no one claims, but toward which the situation is drifting due to lack of global agreement.
The Limits of the CORSIA Mechanism
The emissions compensation mechanism of the International Civil Aviation Organization, known by the acronym CORSIA, is the only existing multilateral tool at the global scale. Its principle: airlines compensate for emissions exceeding the CORSIA baseline, established on 2019 then on 85% of 2019 according to the phase, by purchasing carbon credits. Since 2021, participation is voluntary for the pilot phase. From 2027, obligations cover international flights on state pairs falling within the second phase, determined by CORSIA criteria and applicable exemptions.
The mechanism’s limits are known. It compensates for emissions growth, it does not reduce them in absolute value. It relies on carbon credit markets of uneven quality. And CORSIA coverage depends on participating state pairs and phase rules, including for flights involving the United States and China.
What CORSIA can do: create a price signal that orients investments toward SAFs. What it cannot do: impose a reduction in traffic. CORSIA provides criteria and controls intended to ensure credit integrity, without absolute guarantees being derivable. Strengthening the mechanism in a binding way, with a carbon price integrated directly into the ticket and credit verification standards, is the track several climate economists identify as most effective in the short term. It remains politically blocked due to lack of consensus within the international aviation transport organization.
Who Pays for the Transition and How to Decide
The issue is both technical and distributive. An economy-class passenger on a long-haul flight and a business-class passenger do not have the same carbon footprint per trip. Private jets represent a fraction of passenger traffic but a disproportionate share of emissions per person transported. A uniform carbon price signal weighs proportionally more on the constrained traveler than on the affluent leisure traveler.
The question of SAF R&D financing illustrates another trade-off. Developing e-SAF sectors requires massive public investment, because current production costs far exceed those of fossil kerosene and will not be reduced by the market alone in the short term. These investments compete with other transition needs: electricity grids, storage, building energy efficiency. The decision to allocate public funds to aviation decarbonization rather than other sectors is a political choice, not an automatic consequence of a technology roadmap. It requires public debate that airline industry communication about carbon neutrality commitments tends to bypass.
Economists like Dani Rodrik have formalized this observation in other industrial contexts: industrial policy for decarbonization is arbitrated through prices, norms, and directed public financing, not through intentions alone. Aviation constitutes a particularly clear example, because demand is global, climate externalities are global, and regulatory tools are fragmented between national jurisdictions with different interests and political horizons.
Signals to Follow
Three indicators will reveal, over the next five years, which trajectory aviation actually takes.
The first is the market share of SAFs in total fuel consumed. If this share increases significantly by 2030, the technological bet gains credibility. If it stagnates at a very low level, the organized sobriety scenario becomes unavoidable again, not as ideology but as arithmetic constraint.
The second is the evolution of global air traffic between 2025 and 2030 compared with industry projections. If actual growth exceeds projections, the window for a soft landing closes faster. If it slows, due to a price signal or lower-than-expected demand, room for maneuver widens.
The third is the price of industrially produced e-fuel SAF. Reference costs estimated for e-SAF/PtL far exceed those of kerosene, but they do not necessarily constitute an observed industrial market price. A significant reduction by 2030, thanks to falling electrolysis costs and economies of scale, would change the attractiveness of private investment in these sectors.
These three signals do not tell which policy to adopt. They say which trajectory is underway, independent of declarations. This is a distinction that public debate on aviation tends to neglect, in favor of commitment announcements and voluntary roadmaps. The Shift Project report has precisely the merit of reconstructing the physical and financial mechanics that determine whether these commitments are tenable.
Aviation is a mirror of the energy transition in what it has that is most difficult: a sector where technological alternatives exist but pose scaling challenges, where demand grows in regions that have not historically contributed to the problem, and where decisions must be made collectively among actors with divergent interests. An international binding agreement on traffic volume, with a credible verification mechanism, would constitute decisive progress. This question is not a priority in current negotiations. The question that opens by 2030 is whether physical signals, prices, and climate events will suffice to put it on the agenda before room for maneuver is consumed.
Sources
- Shift Project / Institute for Mobility in Transition, “Flying Without Oil: What Energy Supply for the Aviation Sector?”, February 2026, Link
- Benjamin Fremaux, Montaigne Institute, “Energy 2035: The Trade-offs of Transition”, May 2026, Montaigne Institute
- ReFuelEU Aviation Regulation, European Union, 2023, European Commission, Directorate-General for Energy
- CORSIA Mechanism, International Civil Aviation Organization, ICAO, official documentation
- ATAG (Air Transport Action Group), fleet and traffic projections 2025-2050, ATAG, annual reports
