Can synthetic aviation fuel ever escape the demonstration phase?
Regular refueling of a KLM passenger aircraft at Amsterdam Airport before departure for Hamburg using the e-SAF fuel blend. Image rights: Arnoud Raeven
On 8 June 2026, KLM Cityhopper, INERATEC, Hamburg Airport and MB Energy operated a passenger flight between Amsterdam and Hamburg using a fuel blend containing five per cent synthetic kerosene. The synthetic fuel was produced and hydrotreated by German cleantech company INERATEC, distilled and blended with fossil kerosene by MB Energy at ASG Analytik-Service, and then refuelled into the aircraft at Amsterdam Airport Schiphol.
The flight was presented by the consortium as a demonstration of what is already technically possible. It also pointed to a more difficult question for aviation: can synthetic aviation fuel move beyond limited demonstration flights and become available at the scale required by commercial air travel?
Aviation remains one of the hardest transport sectors to decarbonise. Cars, buses and parts of the rail network can increasingly use electricity directly. Commercial aircraft still rely overwhelmingly on liquid fuels because long-distance flight demands large amounts of energy without adding too much weight.
Aviation's search for a viable alternative
Battery-electric aircraft are making progress in short-range aviation, but current battery technology does not support most commercial passenger flights. Hydrogen aircraft are also under development, yet they would require major changes to aircraft design, fuelling systems and airport infrastructure.
That leaves airlines with a limited number of options.
Sustainable aviation fuel, usually shortened to SAF, has therefore become a central part of many aviation climate strategies. The term covers several types of lower-carbon aviation fuel, including bio-based fuels made from waste and residues, recycled carbon fuels and synthetic aviation fuels made from hydrogen and captured carbon dioxide.
The European Union's ReFuelEU Aviation rules require fuel suppliers to increase the share of sustainable aviation fuel supplied at EU airports. The mandate starts at two per cent in 2025 and rises to 70 per cent by 2050. It also includes a specific requirement for synthetic aviation fuels, starting at 1.2 per cent from 2030.
The company behind the fuel
INERATEC was founded in 2016 as a spin-off from the Karlsruhe Institute of Technology. Its work is based on compact chemical reactor technology that converts hydrogen and carbon dioxide into synthetic fuels and chemicals.
Instead of building only large centralised refineries, the German company has developed modular Power-to-Liquid plants. Power-to-Liquid refers to the process of using electricity to produce liquid fuels. In practice, electricity is used to produce hydrogen, which is then combined with carbon dioxide and processed into synthetic hydrocarbons.
The modular approach is important to the company's strategy. It allows production units to be replicated and deployed where suitable carbon dioxide, hydrogen and energy sources are available.
ERA ONE is the company's most significant project so far.
Located at Frankfurt-Höchst Industrial Park, the plant was inaugurated in June 2025. INERATEC describes it as Europe's first commercial-scale Power-to-Liquid plant and says it can produce up to 2,500 tonnes of e-fuels annually. Its output can include synthetic aviation fuel, e-diesel and feedstocks for the chemical industry.
The plant uses carbon dioxide from biogenic sources and green hydrogen. According to INERATEC, both feedstocks are sourced from the industrial park: carbon dioxide from a biogas plant that processes waste, and hydrogen as a by-product of chlorine production.
For INERATEC, ERA ONE is not only a production site. It is a test of whether synthetic fuel production can move from pilot plants to repeatable industrial operations.
More than a fuel test
The Amsterdam-Hamburg flight, which took place ine arly June, was also a test of the value chain.
INERATEC produced and hydrotreated the synthetic kerosene. MB Energy handled distillation, blending with conventional kerosene, transport and supply to Amsterdam Airport. KLM Cityhopper operated the passenger service. Hamburg Airport participated as the destination airport and infrastructure partner.
As such, the flight therefore demonstrated integration into normal aviation operations and not 'just' the basic feasibility of flying on synthetic fuel. Aircraft have already flown using SAF blends; the harder task is building a supply chain that can make such use routine.
The scale problem
This is where scepticism becomes harder to dismiss.
The technology works. The economics and production volumes remain far less certain.
Global aviation consumes hundreds of billions of litres of jet fuel each year. Current production of synthetic aviation fuel remains very small by comparison.
The consortium behind the Amsterdam-Hamburg flight acknowledged this directly. It noted that only a fraction of the volumes required to meet European 2030 targets is currently in production. It also pointed out that many announced plants have not yet reached final investment decision.
That is the central weakness in the synthetic aviation fuel story.
One commercial-scale plant is a milestone. It is not an aviation fuel system. To change aviation at scale, the sector needs many more facilities, access to large amounts of renewable electricity, reliable hydrogen supply, captured carbon dioxide and enough investment to turn project pipelines into operating plants.
The efficiency debate
Synthetic aviation fuel also faces criticism over energy use.
The process involves several steps. Electricity is used to produce hydrogen. Hydrogen is combined with carbon dioxide. The resulting synthetic crude is processed into usable fuels. Each step involves energy losses.
For critics, that makes synthetic fuel an inefficient use of renewable electricity. Where electricity can be used directly, direct electrification is usually the better option.
That argument is strong for cars, trains and some forms of local transport. It is less straightforward for long-haul aviation.
Supporters of synthetic aviation fuel argue that the relevant comparison is not always between synthetic fuel and direct electrification. For many long-distance flights, the practical alternatives are limited. Synthetic fuel may therefore be less about the most efficient use of electricity and more about finding a lower-carbon option for a sector that cannot easily abandon liquid fuels.
Cost remains a barrier
Cost is another unresolved issue.
Synthetic aviation fuel is still much more expensive than fossil kerosene. That reflects the cost of renewable power, hydrogen production, carbon dioxide sourcing, industrial processing and early-stage plant development.
Industry advocates argue that costs can fall as production scales, plants are replicated and supply chains mature. That has happened in other clean technologies, including solar panels, wind power and batteries.
Fuel production, however, remains tied to physical infrastructure and energy inputs. It cannot scale like software. For airlines, which operate in a competitive market and already face high fuel costs, price will remain a decisive factor.
Without mandates, long-term purchase agreements and public support for early projects, synthetic aviation fuel is unlikely to compete with fossil kerosene on price in the near term.
Europe's industrial challenge
Europe is trying to build a synthetic fuel sector while also cutting aviation emissions, reducing dependence on fossil fuels and creating demand through regulation. Companies such as INERATEC are building production capacity. Airlines are testing supply routes. Fuel companies are adapting infrastructure. Airports are being drawn into the system because refuelling, logistics and certification all have to work in practice.
Public and private financing is also starting to shape the market. In 2025, INERATEC secured a €70 million financing commitment for ERA ONE, including venture debt from the European Investment Bank and grant funding from Breakthrough Energy Catalyst.
The support reflects a wider recognition that hard-to-electrify sectors will need industrial climate technologies, not only digital optimisation or efficiency gains.
Yet the challenge remains physical.
Synthetic aviation fuel needs factories, pipelines, storage, hydrogen, carbon dioxide and electricity. It needs permits, investment decisions and offtake agreements. It also needs time.
Beyond the demonstration phase
The Amsterdam-Hamburg flight did show that synthetic kerosene made in Europe can be produced, processed, blended, transported and used in a regular passenger operation with existing infrastructure.
What it did not show is whether enough synthetic aviation fuel can be produced to make such flights commonplace.
That is now the central question.
Whether synthetic aviation fuel can escape the demonstration phase will be decided less by aircraft than by industrial capacity.
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