A hydrogen-powered plane with the ability to fly as far as from London to Rome has completed its first piloted journey, in a move that could pave the way for zero-carbon routes across Europe.
The aircraft, which was developed by the German company H2FLY, is operated using liquid hydrogen which generates power for the electric motors turning its propeller.
Liquid hydrogen is far lighter than batteries and needs smaller tanks than gaseous hydrogen - potentially giving aircraft a much greater range and more space for passengers and cargo.
Plane makers and engine developers such as Rolls-Royce and Airbus have already tested aircraft powered by gaseous hydrogen.
H2FLY said the use of liquid hydrogen doubles the range of its aircraft to nearly 1,000 miles, the distance from London to Rome, compared with using gaseous hydrogen.
However, the fuel is difficult to manage. Hydrogen is a gas at normal temperatures and must be cooled to -253C to become a liquid, and then stored in insulated cryogenic containers. Hydrogen is also explosive and can easily leak - so rigorous safety measures are essential.
Achievement
Josef Kallo, co-founder of H2FLY, told the Telegraph: "This achievement marks a watershed moment in the use of hydrogen to power aircraft. Together with our partners, we have demonstrated the viability of liquid hydrogen to support medium and long-range emissions-free flight.
"We are now looking ahead to scaling up our technology for regional aircraft and other applications, beginning the critical mission of decarbonising commercial aviation."
Flights lasting up to three hours have taken place at a testing facility in Slovenia.
The system used by the HY4 test aircraft fed the hydrogen into fuel cells which turned it into electricity plus water - which is vented into the air. The absence of fossil fuels means there are no CO2 emissions.
Potential
Pierre Crespi, of Air Liquide Advanced Technologies, which designed the cryogenic tanks holding the liquid hydrogen, said: "This demonstrates the full potential of liquid hydrogen for aviation. Liquid hydrogen can be stored onboard and transported."
In a statement, H2FLY said: "In just a few years, hydrogen-electric aircraft are expected to be able to transport 40 passengers at a time over distances of up to 1,240 miles."
Airbus is developing new hydrogen-powered aircraft with the aim of entering commercial service from 2035 and Rolls-Royce has already proven that hydrogen could power a jet engine following successful ground tests in 2022.
Meanwhile, a leading voice on hydrogen has delivered a grim forecast for one of the UK Government's flagship support schemes.
Chris Jackson told attendees at the Offshore Europe event in Aberdeen that he expects Hydrogen Allocation Round 1 to be a "total failure" due to a lack of joined-up thinking.
He also described the way the support is being implemented as a "shambles".
Westminster announced last month that a total of 17 hydrogen projects, totalling 262MW, had been invited to progress to the next phase of the subsidy scheme.
Amongst those invited to the next stage of negotiations is the Cromarty Hydrogen Project from Storegga.
Contracts are expected to be awarded in the fourth quarter of 2023 for projects targeting first operation in 2025.
But Energy Voice says Mr Jackson, the founder and chief executive of green hydrogen firm Protium, believes it is doomed to fail.