Last Call for Sustainable Aviation

The human body is not made for flying, but mankind has managed to reach the sky and soar through the air by crafting brilliant inventions. 

Nowadays, the global aviation industry can count to more than 30 million commercial flights per year, reaching 35.5 million commercial flights and 4.4 billion passengers carried in 2023. It also supports 86.5 million jobs and accounts for $4.1 trillion (3.9%) of the world’s gross domestic product (GDP). In short, air travel is an essential part of the modern world. It’s what connects the globe and moves humanity forward. However, the benefit has a downside: planes need fuel to fly. 

Kerosene, a fossil fuel derived from petroleum, fuels most modern aircraft. Aviation accounts for approximately 2.5% of global CO₂ emissions and has contributed roughly 4% to global warming so far. These might seem like small numbers, but they’re set to increase, and we can’t afford them.

Global leaders, airlines, manufacturers and stakeholders have pledged to reach a net-zero emissions aviation sector by 2050. A new report from the University of Cambridge’s Aviation Impact Accelerator (AIA) affirms the pledge can be achieved by acting on four key sustainable aviation goals according to its five-year plan. The four goals emphasize the urge to reduce contrails, create more efficient airplanes, thus reducing the amount of fuel needed, ensure fuel sustainability, and invest in “moonshot technologies”. There is a plan, and we know what to do, but execution is tricky, and time is of the essence. 

Ambitions 

In 2020, Airbus unveiled ZEROe, a groundbreaking zero-emission concept aircraft powered entirely by hydrogen. According to their website, this ambitious project, including hydrogen combustion and fuel cell technologies, can reduce aviation’s CO2 emissions by up to 50%. Hydrogen, a clean and abundant resource, offers a promising solution to the aviation industry’s environmental challenges. 

Hydrogen combustion technology uses gas turbines with modified fuel injectors powered by hydrogen, similar to current aircraft. In contrast, hydrogen fuel cells convert the chemical energy of hydrogen and oxygen into electricity. It seems that, for aviation, Proton Exchange Membrane (PEM) and Solid Oxide Fuel Cell (SOFC) technologies are the best candidates. 

Airbus envisions four different hydrogen-powered aircraft models, three of which have hybrid-hydrogen turbofan or turboprop engines and a fuel cell electric regional with LH2. According to the project timeline, the world’s first hydrogen-powered commercial aircraft will be ready by 2035. 

Over the years, ZEROe has been progressing on schedule, even announcing its demonstrator (an A380 MSN1 test aircraft) in 2022 and powering the “iron pod” system on at 1.2 megawatts with hydrogen fuel cells for the first time in December 2023.

Hydrogen is one of the previously mentioned “moonshot technologies,” meaning it presents a great long-term solution, but it is still considered a risky investment. 

Nonetheless, other airlines and manufacturers are developing their hydrogen projects along with testing: Pratt & Whitney is set to demonstrate its hydrogen combustor on a PW127XT turboprop engine under Department of Energy (DOE) funding ; Joby/H2FLY recently demonstrated a flight of its hydrogen-electric concept aircraft ; KLM and ZeroAvia announced a planned liquid hydrogen demonstration flight in 2026 ; and Rolls-Royce, in collaboration with EasyJet, set a “world first” in 2022 by completing the first run of a modern aero engine on hydrogen . 

Boeing, Airbus’ biggest competitor, is choosing a different and more cautious approach: to invest in Sustainable Aviation Fuel (SAF) instead. SAF is jet fuel derived from renewable sources such as plants, waste oils, agricultural residues and Power-to-Liquid technologies to produce e-fuels. As of today, it plays an important role in the decarbonization of the aviation industry, helping companies and stakeholders gradually transition from fossil fuels. 

In 2023, Boeing announced its Cascade Climate Impact Model, a “modelling framework to explore potential scenarios and put data front and centre in the global conversation on reducing aviation’s emissions”, as per its official website. The Cascade model suggests that SAF is the current best pathway to reach net-zero emissions by 2050, along with studying other factors such as traffic growth, fleet renewal, future aircraft, operational efficiency, renewable energy, and market-based measures. Hydrogen is still considered; however, the aviation industry might require a quicker solution – one that SAF offers. 

Several other competitors align with Boeing by prioritizing SAF investments: United Airlines, Emirates, Southwest Airlines, Embraer and, most recently, Air New Zealand. Airbus, despite heavily promoting its hydrogen project, is still pursuing SAF as an alternative.

Reality 

The proper introduction of hydrogen into the aviation industry doesn’t just require the right technology; hydrogen needs its ecosystem. A manufacturer like Airbus needs many collaborators to bring its project to reality. Hydrogen needs to be produced, transported and stored safely. Thus, an efficient ecosystem demands the manufacturer, the airline, the airport, transportation and the production plant to share a perfect synergy, and that is exponentially more complex in execution than it looks on paper. At the start of 2025, reality seems to have set in for Airbus and its airline collaborator Air New Zealand (which deviated towards SAF at the end of 2024): on February 6, 2025, Airbus declared that its commercial hydrogen-powered aircraft could be delayed by a decade. 

The world won’t be able to witness ZEROe before 2040, at the very least. The reason is lack of infrastructure and green hydrogen supply. “We have partnered with several airports which are willing to start introducing hydrogen in their operations ahead of the plane, starting with stationary equipment, cars, buses, and equipment on wheels that is used at airports. That’s the ecosystem’s growth that we need to see happening with sufficient confidence to ensure that entry into service would be successful from the hydrogen supply perspective. That’s not the case today,” Airbus CEO Guillaume Faury told Sustainability Magazine.

Ultimately, SAF is revealed to be the most viable short-term solution for decarbonization, and Airbus announced an investment of its own in collaboration with sustainable fuel technology company LanzaJet. According to the Financial Times, other European airlines are shifting focus away from hydrogen as they work toward a carbon-free future. 

The hydrogen ecosystem isn’t the only concern: regulations regarding safety measures and standards are lacking. In December 2024, the Federal Aviation Administration (FAA) published a roadmap titled “Hydrogen-Fueled Aircraft Safety and Certification Roadmap,” outlining “the current knowledge, key research priorities, and collaborative efforts essential to enabling the safe use of hydrogen in civil aviation aircraft.” This roadmap sheds light on the potential hazards linked to hydrogen (including fire and explosion from uncontrolled leaks). 

With such contrasting information coming from aviation companies, it is hard to determine whether hydrogen truly holds the key to decarbonization or is merely a factor in a sea of many. While companies, stakeholders, and governments are busy deciding if hydrogen is worth a radical investment, air traffic will continue to increase in the coming decades, and GHG emissions will rise. There is hope that SAF and other interventions will be enough to mitigate this increase and successfully bring the industry to its 2050 destination goal. 

Airbus reassures us that hydrogen is still happening, eventually. The plane might have already departed by then.

Elisabetta Fenu