The story in four numbers
The NLR study is significant not as a verdict on which fuel wins but as a structural map of the conditions under which each candidate becomes commercially and technically viable — conditions that differ substantially across the five fuels, placing them at different points on a feasibility curve that does not converge at a single technology by 2050. The firm reads the study's architecture as a confirmation of the portfolio view: aviation's net-zero transition will not be solved by a single substitute for Jet-A but by a fuel mix whose composition is determined by aircraft range category, route geography, infrastructure investment sequence, and the evolution of production costs across a two-decade window. The domestic sourcing imperative that the study addresses — aviation's need, from a US energy security perspective, to reduce dependence on imported petroleum — adds a supply-chain and geopolitical dimension to what would otherwise be a purely technical fuel selection problem, and it explains why ethane and Jet X, which have limited advocates in purely emissions-reduction terms, appear alongside hydrogen and SAF as serious candidates in a NASA-funded programme. The variables that determine the portfolio outcome — green hydrogen production costs, SAF feedstock availability and Power-to-Liquid scale-up, aircraft certification timelines for non-conventional fuels, and airport infrastructure investment — are not independent of each other, and the study's value is in mapping their interdependencies rather than resolving them.
Why aviation's fuel transition is structurally unlike any other sector
The decarbonisation problem in aviation is distinct from the analogous problem in ground transportation in a way that makes direct comparison misleading and that explains why the five-fuel architecture of the NLR study is a structurally correct framing rather than a committee compromise. In ground transportation, the battery electric vehicle has emerged as the dominant technical solution for light passenger vehicles with sufficiently high energy density, falling costs, and improving charging infrastructure to displace the internal combustion engine across the primary use case within a commercially definable timeframe. Aviation does not have an equivalent dominant solution: the energy density requirements of commercial aviation — particularly for long-haul routes where fuel represents 30 to 40 percent of operating cost and where the mass and volume of the fuel load are critical design constraints — set a physical ceiling on what battery technology can achieve, with current and projected battery energy densities in the range of 250 to 400 Wh/kg placing batteries at a factor of roughly twenty below the energy density of Jet-A on a mass basis. This is not a cost-reduction problem or a manufacturing scale-up problem — it is a fundamental electrochemical constraint that makes battery-electric aviation a niche application for short-haul routes and urban air mobility rather than a solution to aviation's primary emissions challenge. The consequence of this constraint is that aviation's transition requires liquid or gaseous fuels with energy densities in a range compatible with existing or feasibly modified aircraft architecture, and the candidate field is narrow: sustainable aviation fuels that are chemically similar to Jet-A and drop-in compatible with existing engines and infrastructure, hydrogen that offers superior gravimetric energy density but severe volumetric penalties, and cryogenic hydrocarbon alternatives including LNG that occupy the middle ground between conventional jet fuel's infrastructure compatibility and hydrogen's lower emissions profile. The addition of ethane and a synthetic hydrocarbon designated Jet X in the NLR study reflects the domestic sourcing dimension: the US has abundant ethane production from natural gas processing in the Permian Basin and other shale formations, making ethane a candidate primarily from a resource availability and energy security perspective rather than from an emissions reduction perspective, and Jet X represents the class of Fischer-Tropsch and Power-to-Liquid synthetic hydrocarbons that could be produced from domestic feedstocks — coal with carbon capture, natural gas with CCS, or biomass — at costs that are competitive with imported petroleum under certain carbon pricing and energy security scenarios. The NLR study's contribution is to bring these candidates into a common analytical framework that assesses them against the same operational, environmental, and infrastructure variables, allowing comparison across dimensions that individual fuel advocates typically do not address with equal rigour.
01 · The five candidates — what NLR is measuring and why each fuel is in the study
The five fuels assessed in the NLR study represent a deliberate coverage of the full candidate space for commercial aviation rather than a selection of the most technically promising alternatives — a design choice that reflects both the study's domestic sourcing mandate from its NASA funding context and the genuine uncertainty about which fuel combinations will prove most deployable at scale by 2050.
Sustainable aviation fuel encompasses a broad family of bio-derived and synthetic hydrocarbon fuels that share the drop-in compatibility with existing Jet-A infrastructure as their defining commercial advantage. The dominant commercial pathway, HEFA (Hydroprocessed Esters and Fatty Acids), converts vegetable oils, used cooking oil, and animal tallow into synthetic paraffinic kerosene through hydroprocessing — a well-established chemical process that produces a fuel with lifecycle CO2 reductions in the range of 50 to 80 percent depending on the feedstock provenance and regional carbon intensity of the hydrogen used in the process. The emerging pathway, Power-to-Liquid or e-SAF, uses green hydrogen produced through water electrolysis and captured CO2 to synthesise synthetic hydrocarbons through Fischer-Tropsch or methanol-to-jet processes — achieving near-zero lifecycle emissions under scenarios where the hydrogen is produced with renewable electricity and the CO2 is captured from direct air capture rather than industrial point sources. Both pathways are technically proven; the constraint is production scale and cost relative to conventional jet fuel, with current global SAF production in the range of 300,000 to 500,000 tonnes per year against global jet fuel demand of approximately 300 million tonnes per year. Hydrogen enters the study as the lowest-lifecycle-emissions option for combustion-based aviation — combusting hydrogen in a modified gas turbine produces water vapour rather than CO2, though the contrail and nitrogen oxide effects of hydrogen combustion at altitude remain an active research question. The technical challenge of hydrogen aviation has two independent dimensions: the aircraft design problem, which requires developing airframes with cryogenic fuel tanks capable of storing liquid hydrogen at approximately -253°C in volumes four times larger than conventional Jet-A tanks for equivalent energy, and the airport infrastructure problem, which requires replacing the jet fuel storage, distribution, and dispensing infrastructure at airports with liquid hydrogen equivalents that do not yet exist at commercial airports anywhere in the world. Liquefied natural gas is a transitional candidate: its storage requirements (-162°C, which is technically simpler than hydrogen's -253°C cryogenic requirements) and its energy density (approximately 22 MJ/L against Jet-A's 34.5 MJ/L) position it between hydrogen and conventional jet fuel in terms of infrastructure challenge, while its lifecycle emissions depend heavily on upstream methane leakage rates and the proportion of bio-methane or synthetic methane in the supply. Ethane and the synthetic hydrocarbon Jet X are the candidates whose presence in the study is most directly explained by the domestic sourcing mandate: both can be produced from abundant US domestic resources — ethane from natural gas processing and Jet X from Fischer-Tropsch synthesis using domestic coal, gas, or biomass — and their inclusion reflects the study's assessment of fuel security alongside fuel emissions.
The five-fuel architecture is not intellectual indecision about which alternative wins — it is a structurally honest acknowledgement that aviation's transition requires different fuels for different route categories, geographies, and timelines, and that the industry cannot afford to foreclose on any credible candidate until production costs, infrastructure investment, and aircraft certification timelines have resolved the relative feasibility of each pathway through the 2030 to 2040 window.
02 · Hydrogen aviation — the 2050 feasibility question and the barriers that define it
The question the NLR study asks about hydrogen — whether it can fuel aviation by 2050 — is precise in a way that its headline rendering as a yes/no question obscures: the answer is almost certainly yes for a subset of aviation by 2050, and almost certainly not for the majority of aviation by 2050, and the analytically interesting question is which subset and under what conditions.
Airbus has publicly committed to entry-into-service of a hydrogen-powered commercial aircraft by 2035 under the ZEROe programme, targeting short-to-medium-haul routes of under approximately 2,000 kilometres where the volumetric penalty of liquid hydrogen tanks is manageable within an aircraft redesigned from the outset around a central fuselage-mounted cryogenic tank or under-wing pod configuration. The certification and fleet penetration timeline from a 2035 entry-into-service to meaningful market share by 2050 is fifteen years — comparable to the timeline for any major aircraft programme from first commercial flight to significant fleet penetration — suggesting that hydrogen could realistically supply a meaningful but not dominant share of short-haul aviation capacity by 2050, concentrated in the routes and airport pairs where cryogenic infrastructure investment has been made. The critical variable is green hydrogen production cost: the levelised cost of green hydrogen produced through water electrolysis powered by renewable electricity has fallen from approximately $5-6 per kilogram in 2020 to approximately $3-5 per kilogram in 2024 in favourable renewable energy locations, and industry projections for cost reduction trajectories under scaling scenarios suggest green hydrogen reaching approximately $1-2 per kilogram by 2035 to 2040 — but the confidence interval on that projection is wide, and the delivered cost to aircraft at airport — which includes liquefaction (highly energy-intensive, consuming approximately 30 percent of the hydrogen's energy content), storage in cryogenic tanks, and airport distribution — adds substantially to the fuel cell price. The airport infrastructure barrier is arguably more binding than the aircraft design barrier for the 2050 timeline: Airbus can design a hydrogen aircraft and certify it within a fifteen-year development programme, but the conversion of a major hub airport from Jet-A fuelling infrastructure to liquid hydrogen fuelling infrastructure is a multi-billion-dollar capital project with a ten-to-fifteen-year permitting, construction, and commissioning timeline that requires coordinated commitment from airport operators, airline customers, and government agencies simultaneously. The NLR study's contribution to this question is in establishing the conditions — green hydrogen cost trajectory, airport infrastructure investment sequence, and aircraft certification programme — under which hydrogen aviation transitions from a technically credible concept to a commercially deployable reality within the 2050 window, and in mapping the route categories and market segments where those conditions are most likely to be met first.
| Fuel | Volumetric energy density | Lifecycle CO2 reduction | Drop-in compatible | Infrastructure readiness | 2050 role |
|---|---|---|---|---|---|
| Conventional Jet-A | ~34.5 MJ/L (baseline) | Baseline (0%) | Yes | Fully deployed globally | Declining residual share |
| SAF (HEFA) | ~33–34 MJ/L | 50–80% (feedstock-dependent) | Yes (up to 50% blend) | Limited commercial scale | Dominant transition fuel |
| SAF (Power-to-Liquid) | ~33–34 MJ/L | ~90–95% (green H2 + DAC) | Yes (up to 50% blend) | Pre-commercial | Growing share post-2035 |
| Liquid hydrogen | ~8–10 MJ/L (~4x volume penalty) | ~85–100% (green H2) | No (aircraft redesign required) | No commercial airports | Short/medium-haul niche |
| LNG (bio / synthetic) | ~22 MJ/L | 20–60% (source-dependent) | No (modified aircraft) | Limited (cargo operators) | Transitional / regional |
| Ethane | ~16 MJ/L | ~15–30% vs. Jet-A | No (significant modification) | No aviation deployment | Domestic security niche |
| Jet X (synthetic hydrocarbon) | ~32–34 MJ/L | 40–90% (production-dependent) | Yes (drop-in FT blend) | Pre-commercial | Domestic energy security fuel |
03 · SAF at scale — the cost, feedstock, and infrastructure constraints on the dominant pathway
Sustainable aviation fuel is the consensus dominant pathway for aviation's near-term decarbonisation precisely because it is drop-in compatible with existing engines, aircraft, and airport infrastructure — but the constraints on scaling SAF from its current fraction of a percent of global jet fuel demand to the 65 percent share that IATA's net-zero roadmap assigns to it by 2050 are structural rather than merely financial, and the NLR study's engagement with SAF alongside less developed alternatives is a recognition that SAF alone cannot close the 2050 gap on current trajectory.
The feedstock constraint is the binding near-term limit on HEFA-based SAF, the most commercially mature production pathway. The primary HEFA feedstocks — used cooking oil, tallow, and animal fats — have limited global supply that is already substantially committed to biofuels across transport sectors, and the vegetable oil feedstocks that could supplement them compete directly with food systems for agricultural land in a way that introduces life-cycle emissions complications from land use change that can erode or eliminate the fuel's emissions advantage. Published estimates of global sustainable HEFA feedstock availability place the ceiling for HEFA-based SAF production at approximately 30 to 50 million tonnes per year in most scenarios — a substantial improvement from current production but less than 20 percent of projected 2050 aviation fuel demand, establishing a feedstock ceiling that makes HEFA alone insufficient for the transition even in optimistic scenarios. The pathway that can overcome the feedstock ceiling — Power-to-Liquid synthesis from green hydrogen and captured CO2 — requires electricity inputs of approximately 20 to 25 MWh per tonne of SAF produced, making PtL SAF's production cost and scalability directly dependent on the cost trajectory of renewable electricity and the development of direct air capture of CO2 at commercial scale and cost. In the most optimistic renewable electricity and DAC scenarios, PtL SAF production costs converge toward conventional jet fuel costs somewhere in the 2040 to 2050 window — which means the transition decade will be characterised by a PtL SAF that is still significantly more expensive than Jet-A and that requires either carbon pricing, mandates, or blending obligations to drive demand beyond the voluntary commitments of sustainability-motivated airlines. The blending mandate architecture that the EU has deployed through RefuelEU Aviation — requiring minimum SAF blending fractions of 2 percent in 2025 rising to 70 percent in 2050, with a sub-mandate for PtL SAF rising to 35 percent by 2050 — is the regulatory instrument that bridges the cost gap between SAF and Jet-A by creating mandatory demand that allows production investment to proceed ahead of cost parity. The US SAF Grand Challenge targets 3 billion gallons of SAF per year by 2030 and full replacement of conventional jet fuel by 2050 through a combination of tax incentives, grants, and voluntary commitments from airlines and producers — a structurally different policy approach from the EU's mandates that reflects different assumptions about the role of government in technology deployment, and whose adequacy for reaching the scale targets is assessed differently by different analysts.
The constraint on SAF in 2050 is not primarily a technology constraint — the production pathways are established. It is a capital deployment constraint in Power-to-Liquid infrastructure and a feedstock availability constraint in HEFA that requires the policy environment to resolve the cost gap between SAF and Jet-A before production investment reaches the scale the transition requires. The NLR study's inclusion of four additional candidates alongside SAF reflects the risk that the policy environment does not resolve that gap on schedule.
04 · The domestic sourcing variable — how US energy policy reshapes the fuel portfolio calculus
The domestic sourcing imperative that the NLR study addresses — explicitly framed in the meta description as aviation seeking domestic fuel sources beyond conventional jet fuel — introduces a dimension to the fuel portfolio analysis that is largely absent from purely emissions-focused assessments: the intersection of aviation decarbonisation with US energy security policy, which currently prioritises domestic production of energy across all sectors as a strategic objective independent of the climate motivation for alternative fuels.
The US aviation sector consumes approximately 40 billion litres of jet fuel per year, drawing on a global petroleum market whose supply is exposed to geopolitical disruption from Middle Eastern, Russian, and other non-US producers. The energy security argument for domestic alternative aviation fuels is structurally similar to the argument for domestic petroleum production: reducing the fraction of aviation fuel that originates from imported petroleum reduces the sector's vulnerability to supply disruptions and price volatility in international commodity markets. This argument applies with different force to different fuel candidates. HEFA-based SAF from US domestic feedstocks — primarily soybean oil, corn oil, and tallow from US agricultural operations — provides a domestic supply advantage over imported petroleum but is constrained by the agricultural land and food system competition dynamics described above. Ethane, produced in abundance as a byproduct of US natural gas processing in the Permian Basin, Marcellus Shale, and other formations, provides a genuinely domestic and currently abundant feedstock that does not compete with food systems — but whose conversion to aviation fuel requires process development and aircraft compatibility demonstration that is substantially behind HEFA and synthetic alternatives in readiness. The domestic security case for ethane is strongest in scenarios where its lifecycle emissions are managed through either efficiency improvements in production and conversion or, in longer-horizon scenarios, through integration with carbon capture — making it a credible near-to-medium-term security-motivated fuel that is not primarily justified on climate grounds. Jet X, as the study's synthetic hydrocarbon candidate, represents the class of fuels producible from domestic coal with carbon capture and storage, domestic biomass, or domestic natural gas with CCS — technologies that have been commercially demonstrated in the Fischer-Tropsch context (Sasol in South Africa, several US coal-to-liquids demonstrations) but that require substantial scale-up investment and whose competitiveness depends on both the cost of CCS and the price of alternative fuels. The domestic sourcing variable reshapes the portfolio calculus most significantly at the margin: in a world where climate policy is the dominant driver of aviation fuel selection, hydrogen and PtL SAF are the clear long-term winners; in a world where energy security is co-equal with climate policy, ethane and Fischer-Tropsch Jet X from domestic resources gain portfolio weight that pure emissions analysis would not assign them, and the five-fuel architecture of the NLR study is the analytical consequence of taking both objectives seriously simultaneously rather than subordinating security to climate or climate to security.
The near-term decade is structurally defined by the gap between SAF's production cost and Jet-A's market price, and by the policy instruments — blending mandates, production tax credits, and procurement commitments — that are being deployed to bridge that gap. The EU's RefuelEU Aviation mandate creates binding demand that de-risks SAF production investment within the European market; the US SAF Grand Challenge creates incentives but not mandates, leaving a larger uncertainty band around US SAF deployment pace. The most commercially significant decision in this window is the investment commitment in PtL SAF production infrastructure — the pathway that can overcome the feedstock ceiling on HEFA-based SAF — which requires capital commitments in the 2025 to 2030 window for capacity that comes online in the 2033 to 2038 window. Whether those commitments are made at scale depends on the policy environment's resolution of the cost gap, making the 2025 to 2030 policy window arguably the most consequential in aviation's transition timeline despite its distance from 2050.
The later transition decade is defined by whether a commercially certified hydrogen aircraft enters revenue service in the 2035 to 2038 window and begins accumulating the operational experience and fleet penetration that would allow meaningful market share by 2050 — and by whether the airport infrastructure investment that hydrogen aviation requires has been made at a sufficient number of airports to create a viable network of hydrogen-fuelled routes. The portfolio convergence question — whether the five-fuel architecture simplifies into a two or three-fuel system as cost and technology trajectories resolve — will become legible in this window, as PtL SAF cost trajectories, hydrogen aircraft certification outcomes, and carbon pricing evolution determine which candidates have sustainable commercial positions and which are transitional or security-motivated options that fade as the primary alternatives scale. The firm's assessment is that the most likely 2050 outcome is a three-fuel system: PtL SAF dominant on long-haul routes, liquid hydrogen on short-to-medium-haul routes where airport infrastructure has been built out, and HEFA-based SAF as a declining but still significant fraction of the blend in markets where PtL SAF production is not yet at full scale.
What the five-fuel study tells the capital markets about aviation's transition architecture
The NLR study's analytical contribution is the placement of hydrogen in a comparative framework alongside fuels that share its 2050 deployment horizon but not its technical architecture — and the finding, implied by the five-fuel structure rather than stated as a conclusion, that no single candidate dominates the field across all dimensions of the evaluation. SAF wins on infrastructure compatibility; hydrogen wins on long-term lifecycle emissions potential for combustion-based aviation; LNG and ethane win on near-term domestic production availability in a US energy security context; Jet X wins on drop-in compatibility from domestic production feedstocks. The portfolio that emerges from combining these partial winners is not the analytical failure of a study that could not choose — it is the correct description of an industry whose capital stock, route geography, and infrastructure constraints require different solutions in different segments.
For capital markets, the study's structure reinforces the firm's view that aviation's decarbonisation is a multi-decade, multi-asset-class investment thesis rather than a single technology trade. The investable themes run across renewable electricity for green hydrogen and PtL SAF production; direct air capture scale-up for the carbon feedstock of PtL synthesis; feedstock development for HEFA-based SAF including advanced agricultural residue and waste streams; aircraft programme development for hydrogen-compatible airframes; airport infrastructure conversion for cryogenic fuel handling; and the regulatory and carbon pricing mechanisms that bridge the cost gap between all alternatives and conventional Jet-A. Each of these themes has a different maturity level, a different risk profile, and a different timeline to commercial scale — and the NLR study's framing clarifies which variables resolve first and in what sequence the capital deployment should follow.
The firm's assessment of the NLR study is that its headline question — can hydrogen fuel aviation by 2050 — is less important than the structural answer that the five-fuel framework implies: aviation reaches 2050 not by selecting hydrogen or SAF or any single candidate but by building a portfolio across all five in proportion to their respective progress on cost, infrastructure readiness, and policy support over the transition decade. The capital allocation question is not which fuel wins but which transition constraints — production cost, infrastructure investment, policy certainty — resolve first, and in what order that resolution makes deployment commercially compelling for each candidate in its respective market segment. That is a more useful frame for investors and operators than a binary answer to the question the headline poses, and it is what a serious aerospace research programme produces when it takes the problem's full complexity seriously.
Sources: Netherlands Aerospace Centre (NLR) published programme documentation and aerospace research; NASA Aeronautics Research Mission Directorate published aviation energy studies; IATA Net Zero 2050 roadmap and SAF production tracking reports; ICAO Carbon Offsetting and Reduction Scheme (CORSIA) documentation; EU RefuelEU Aviation regulation (Regulation EU 2023/2405) and Fit for 55 package; US SAF Grand Challenge published programme targets and progress reports; Airbus ZEROe programme documentation; published lifecycle assessment literature for aviation fuel alternatives (Argonne National Laboratory GREET model, MIT Aviation Sustainability Center research); IEA Hydrogen Projects Database; US Energy Information Administration natural gas liquids production data. This note is for informational purposes only and does not constitute investment advice.
