We proceed with our series of stories based on the IATA Net Zero Roadmap, where progress and plans for Sustainable Aviation Fuel and Hydrogen Fuel Cells are considered up to the year 2030.
Figure 1, which follows (Aircraft Technology Net Zero Roadmap), highlights the planned and anticipated items of how Sustainable Aviation Fuel (SAF) and Hydrogen technologies will be advanced in the 2023 – 2030 timeline.
The specific discussions in this web story will address items 5 and 6 (see Figure 1, left column), which relate to the Milestones and Descriptions for validating 100% SAF-compatible seals and metering, in addition to Entry Into Service for regional jets outfitted with Hydrogen Fuel Cells.
Figure 1: IATA Net Zero, SAF and Hydrogen Aircraft 2023 – 2030 timeline
Towards Net Zero: The Future of Aviation Fuel
The International Air Transport Association (IATA) has outlined a roadmap to achieve net-zero carbon emissions by 2050. Central to this plan is the widespread adoption of Sustainable Aviation Fuel (SAF), along with advancements in hydrogen propulsion and aircraft efficiency. The period from 2023 to 2030 marks a critical phase for testing, scaling, and certifying these alternative fuels and technologies.
SAF can be divided into two main categories: paraffinic SAF and fully formulated SAF. Paraffinic SAF, which currently dominates the market, lacks certain hydrocarbons, especially aromatics, that are found in conventional jet fuel. This absence of aromatics creates compatibility challenges with existing aircraft systems. Notably, aircraft rely on nitrile seals in fuel lines and tanks that require these aromatics to provide conditioning services so as to remain flexible and leak-free. Additionally, fuel metering systems are calibrated for fluids with specific density and energy characteristics, which paraffinic SAF doesn’t fully match. As a result, paraffinic SAF must be blended with traditional jet fuel to meet the certification standards, as defined by ASTM and the Energy Institute’s JIG 1533 standard.
Fully formulated SAF, in contrast, mimics conventional aviation fuel in both composition and performance. It includes aromatics and all necessary hydrocarbons, making it a true drop-in fuel without requiring any modifications to aircraft. ASTM is currently developing standards to allow aircraft to operate on 100% fully formulated SAF, with completion expected by 2030. Blends of up to 50% SAF are already used with commercial and military aircraft engines. These blends are fully compatible and do not affect seals or metering systems. A SAF process optimization diagram is presented in Figure 2, which indicates the technology roadmap which will be used and applied for this process optimization.
Figure 2: SAF Process Optimization – Technology Roadmap
Aircraft manufacturers have pledged that all new civil aircraft will be compatible with 100% paraffinic SAF by 2030. Ground and flight tests are currently underway to achieve this, focusing on both unblended and blended SAF. The next critical step is to validate seals and fuel metering systems for complete SAF compatibility. Considerable discussion on SAF fuel metering involves automatic fuel data validation, which would be a game-changing innovation and a critical requirement for any onboard technology provider. This feature allows users to ‘close out’ their data daily by cross-referencing, reconciling, and validating fuel data from multiple sources to ensure its accuracy and reliability. Much-needed benefits are derived here for aviation businesses and their stakeholders, such as improved data integrity, enhanced operational efficiency, reduced fuel costs, better regulatory compliance, and more accurate environmental impact reporting would result. Five advantages of Automatic Fuel Data Validation are indicated to be as follows:
- Data is cross-referenced from multiple sources. By cross-referencing this data, the system can detect inconsistencies and discrepancies, which can be further investigated and resolved to ensure data accuracy. A key challenge that the production of SAF presents is that the source of these feedstocks is not fully determined yet. Some adherents propose using oilseeds, which would reduce the amount of available land for arable agriculture. This is a food security concern in some regions that have food security concerns and consequently requires a public policy discussion. In other cases, the agricultural, woodlot, and industrial wastes are quite varied, such that SAF production methods and blends may not resemble other sources.
- Daily reconciliation and validation. Automatic fuel data validation often includes reconciliation processes that compare and match fuel transactions, consumption records, and invoices. Again, this identifies any inaccuracies or discrepancies in the data, ensuring that only reliable information is used for decision-making and reporting. Additionally, validation algorithms can be employed to check the consistency of data, such as verifying fuel density values or identifying outliers in fuel consumption patterns.
- Minimizes human error. We all understand that manual data entry and processing are prone to human error, which leads to inaccurate information and negatively impacts decision-making. Automated fuel management and validation minimize this risk by automatically capturing, processing, and validating fuel data. This reduction in manual processes not only improves data accuracy but also saves valuable time and resources in critical aviation management regimes.
- Automated integrity checks and alerts. Automatic validation of fuel data should include built-in data integrity checks and alerts that notify relevant personnel of any potential issues, such as missing data, data discrepancies, or unusual fuel meter movements. These alerts enable timely detection and resolution of issues, maintaining high data integrity and trust across the global aviation regime.
Despite progress to date in proving these needs and capabiliies, challenges remain. Scaling SAF production is essential, yet feedstock limitations and the time needed to develop synthetic fuel pathways may constrain supply. As SAF use ramps up globally, its mix of feedstocks and production methods will result in varying levels of lifecycle emissions. Therefore, ongoing efficiency improvements in aircraft design and operations are also crucial. These enhancements could reduce the fleet’s energy use by up to 10% by 2050, further magnifying the environmental benefits of clean fuels.
Technology Readiness levels for various components in this regime range from TRL 5 (validation in relevant environment) to TRL 9 (actual system flight proven). These wide bands in component technology readiness will all need to be moved up to TRL 9. (See Reference 1, below)
Ultimately, SAF will be the backbone of emission reductions for the existing and near-future global fleet, estimated to grow from 30,000 aircraft in 2019 to 65,000 by 2050. Pairing SAF with hydrogen, batteries, and continuous technological innovation forms the multi-pronged strategy necessary for aviation to achieve net-zero emissions by mid-century.
Note to SAF
Paraffinic Sustainable Aviation Fuel (SAF) refers to a type of SAF that is predominantly composed of Synthetic Paraffinic Kerosene (SPK). SPK is a low-carbon, renewable jet fuel made from sustainable feedstocks like agricultural byproducts. It’s designed to be a drop-in fuel, which can be blended with conventional jet fuel without requiring significant changes to aircraft engines or fueling infrastructure. Being paraffinic refers to the fact that the chemistry of this fuel is based on long-chain hydrocarbons. These fuels are produced from non-petroleum sources.
The aromatic portion of current aviation fuel consists of hydrocarbon molecules containing at least one ring of six connected carbon atoms. Aviation fuels as currently distilled can contain between 8% to 25% aromatics.
While SAF plays a pivotal role, it alone cannot deliver the emissions reductions needed by the aviation industry. Alternative technologies—particularly hydrogen and battery-electric propulsion—must complement SAF adoption. These zero-carbon energy carriers offer additional paths to reducing aviation’s environmental footprint. However, hydrogen-powered aircraft will likely make up only a small portion of the fleet by 2050. Here is the IATA and others’ take on hydrogen flight will proceed.
Hydrogen Takes Flight: The Future of Regional Jets
As aviation races toward its net-zero goals, regional jets are poised to play a pivotal role in the adoption of hydrogen-powered flight. While much of the industry’s attention has been focused on sustainable aviation fuel (SAF), hydrogen, particularly in fuel cell form, is emerging as a zero-emission game-changer for sub-regional and regional aircraft.
Hydrogen fuel cell (HFC) technology is already being tested and implemented in small aircraft, with companies like ZeroAvia and Universal Hydrogen leading the charge. These innovators are retrofitting existing 9- to 19-seat turboprops with hydrogen-electric powertrains, with entry into service expected after 2025. This marks the beginning of a crucial shift: replacing fossil fuels with a new energy carrier, hydrogen.
Figure 3 shows a comparison between the ZA600 Hydrogen Fuel Cell propulsion system vs a conventional regional jet using the typical gas turbine engine.
Figure 3: A Comparison of HFC and Gas Turbine Regional Aviation Systems
The next frontier is scaling hydrogen propulsion for larger regional aircraft, particularly turboprops and small jets in the 30- to 90-seat range. These aircraft serve short-haul routes that make up roughly 8% of global flights, but they also account for over 170 million seat movements annually. Retrofitting this fleet with HFC systems could reduce carbon emissions by more than 170 Mt CO2e, equivalent to the annual emissions of an entire industrialized nation.
One reason regional jets are ideal testbeds for hydrogen is that many fly routes under 400 nautical miles—well within the range of early hydrogen-powered aircraft using gaseous storage. Aircraft like the ATR 72 and Dash 8-400, though capable of 800+ NM, often operate on far shorter flights, allowing room to trade range for clean fuel technology. In fact, 95% of the sub-20-seat aircraft market could be served with current hydrogen-electric systems, using around 60–70 kg of compressed hydrogen per trip.
Figure 4: Illustration of the ATR 72-600
The above Figure 4 shows – Modelling of a battery-supported fuel cell electric power train topology for a regional aircraft – Scientific Figure on ResearchGate. Available from here:
Still, challenges remain. Gaseous hydrogen has low volumetric energy density, making it difficult to store enough fuel for longer flights without major design changes. That’s where liquid hydrogen (LH₂) becomes essential. With nearly three times the volumetric density of compressed hydrogen, LH₂ allows for longer ranges and greater passenger capacity. However, storing it requires cryogenic tanks, which must be insulated, lightweight, and capable of handling boil-off management.
These storage tanks will also need to integrate with advanced thermal systems, possibly even functioning as heat sinks during energy-intensive phases like takeoff. New designs, such as blended wing bodies and modular fuel tanks, may also help solve some of these integration issues.
The regional market is an excellent proving ground for technologies destined for larger aircraft. Many components—such as high-efficiency fuel cells, electric motors, and hydrogen management systems—will evolve in this space before fully scaling up to narrowbody and even widebody aircraft.
New aviation market entrants such as ZeroAvia are developing certified hydrogen powertrains like the ZA600 and forming partnerships with OEMs like Textron Aviation. As a result the commercial pathway is rapidly forming. The ZA600 system, for instance, promises significant operational savings: up to 51% lower cost per seat mile, 10x lower maintenance costs, and a nearly 80% reduction in CO2 emissions compared to jet fuel. (See Figure 3) As these technologies mature, regional jets will do more than just fly clean—they’ll pave the runway toward a truly hydrogen-powered future for aviation.
Reference 1: : https://doi.org/10.1016/j.jclepro.2024.141472