While a number of companies are hard at work researching and developing hydrogen propulsion systems for more sustainable aircraft, commercial airlines around the world are starting to plan for future operations with hydrogen-powered aircraft. They face significant logistical and business challenges to make this transition work.

ZeroAvia, a California-based company developing hydrogen powertrains to convert existing airliners, recently held its annual Hydrogen Aviation Summit, where executives from British Airways, United Airlines, Air France, and KLM discussed how airlines will go about incorporating hydrogen-powered aircraft into their fleets.

“Hydrogen is going to be a really key part of our pathway to net zero,” Carrie Harris, British Airways’ director of sustainability, told the worldwide audience. “We're aiming to get to net zero by 2050, or ideally sooner.”

For the UK carrier, as is the case for other airlines, the key to successfully introducing hydrogen-powered aircraft into their fleet will be to make sure that flights remain profitable—and that they can carry enough passengers. The first hydrogen-powered aircraft on the market will be too small to provide a viable and profitable alternative for a vast majority of routes that operate today. For example, ZeroAvia’s first hydrogen-electric powertrain, the 600-kilowatt ZA600—which is expected to enter service in 2025—is designed to support 10- to 20-seat airframes.

From a research and development perspective, “the expectation at the moment is that we start with smaller aircraft and kind of gradually scale up,” Harris said. “When we looked at that for our operation though, it's not really viable. And so for [British Airways], we're really remaining focused on the kind of 70-plus seater.”

According to Harris, a hydrogen aircraft with 70 or more seats could operate from some of British Airways’ smaller hubs, like London City. In the interim, “it might well be that we see hydrogen propulsion introduced on the short commuter, island hopper type routes, and then later scaling up,” she said. “But what I'm really hoping for is that we'll see a breakthrough and we get the opportunity to potentially retrofit onto existing airframes,” Harris explained. “I think for our operation, we're definitely more interested in kind of like-for-like replacement of single-aisle, short-haul aircraft.”

The Path to Net-Zero Emissions

Both British Airways and United Airlines have been making early investments in hydrogen and other “green” initiatives, such as sustainable aviation fuels. But the two companies have taken different approaches to reach their goal of achieving net-zero emissions by 2050. For example, British Airways plans to use carbon offsets, while United has pledged not to use any carbon offsets.

“In the short term, [British Airways is] kind of investing in operational efficiency and putting a real focus on that right now, but also bringing in carbon removals, carbon offsetting for our domestic operations, and working with customers and how they can take part in carbon offsets and removals,” Harris explained.

Instead of relying on carbon offset programs to reduce its carbon footprint, United Airlines “is looking at technologies and investing in companies that are really developing ways to truly be no-emission, 100 percent green,” said Ed Espiritu, senior manager of corporate development at United Airline Ventures.

“At United, we're taking a multi-pronged approach to that agenda to achieve that goal, so that includes investing into sustainable aviation fuel companies, battery technologies, and of course, hydrogen,” Espiritu added. “But at the end of the day, we want to find companies that can create value both environmentally as well as financially.”

United’s Hydrogen Strategy Considers the U.S. Pilot Shortage

Espiritu explained that United’s strategy for introducing hydrogen aircraft will involve “upgauging” the size of the aircraft in its fleet. For example, the airline may begin its hydrogen-powered operations using small, 50-seat airplanes before swapping those out for larger, 76-seat airplanes, which will be followed by larger narrow-body airliners that can seat more than 100 passengers.

United decided on this strategy for two reasons. For one, larger fleets of smaller aircraft become more expensive to maintain over time, so operating smaller fleets of fewer, larger aircraft is more cost-effective. The other reason is the current pilot shortage in the United States. The pilot shortage, Espiritu explained, is “really making it hard for our regional partners to operate some of their routes, particularly those of the smaller gauge 50-seaters, and so that's driving this move toward larger state aircraft.”

However, Espiritu added that due to the lower maintenance costs associated with hydrogen-powered airplanes compared to traditional aircraft, and depending on how the pilot shortage plays out in the future, it may be economically viable to down-gauge and reintroduce more of the smaller hydrogen-powered aircraft in the longer term.

“Based off of the laws of supply and demand, once we are enticing a lot of regional pilots to become pilots for larger gauge aircraft, that'll increase the supply, and that will allow for new routes to then cycle through, which would then include going back down gauging, if you will, to the 50 seat market,” Espiritu said. “And by the time that cycle plays itself out, there could be a place for a hydrogen retrofitted solution.”

Maintenance, Repair, and Overhaul in the Hydrogen Era

While ZeroAvia is largely focused on researching and developing the technology required to introduce hydrogen propulsion systems for aircraft, the company is also looking to the future to plan for maintenance, repair, and overhaul (MRO) services for future hydrogen-powered fleets.

Last week ZeroAvia announced that it has signed a memorandum of understanding with Air France Industries KLM Engineering and Maintenance (AFI KLM E&M). The subsidiary of the major European airline group provides maintenance, repair and overhaul services for more than 200 carriers around the world, to develop the capabilities and knowledge that will be required to service future hydrogen-powered airliners. In October, the company announced a partnership agreement with Ampaire, which is working to convert existing regional airliners to hybrid-electric propulsion.

Air France KLM's engineering division is looking to provide maintenance, repair and overhaul support for new electric aircraft. (Image: Air France KLM)

“We will work with our partners in AFI KLM E&M to assess the training needs that will be required for technicians involved in retrofit and maintenance, explore data analytics and prognostics, and work towards possible retrofit and MRO partnerships to support ZeroAvia powertrains globally,” ZeroAvia said in a statement.

Derk Nieuwenhuijze, AFI KLM E&M’s v-p of strategy, marketing and communications, said during the ZeroAvia summit that original equipment manufacturers (OEMs) “will need a lot of support. So, coming from the maintenance side, we are already looking into how do you maintain such an aircraft? What kind of logistics does it need in terms of parts and support? What kind of training do you need for all the different checks that you will have for the warranty, the safety and the flight safety?”

Nieuwenhuijze added that AFI KLM E&M is working with several different parties to reduce the cost of maintaining hydrogen-powered airliners using “predictive maintenance” and other smart functions associated with new, high-tech aircraft.

“Everything that we're adding or changing to the aircraft will be much more modern than than any of the previous ones, so there will be more sensors, more knowledge, more data on these aircraft than ever before,” Nieuwenhuijze said. “And what we are already seeing in the platforms of the 787 and A350 that will continue [is] that you have such smart aircraft that, with predictive maintenance and all of the tools that you can develop around that, you can actually really drive and steer also the cost of such an aircraft further down.”

Hydrogen-Powered Aircraft on the Horizon

ZeroAvia says it has collected letters of intent from at least 15 different airlines interested in adding hydrogen-powered airplanes to their fleets, and the company has already begun flight testing with its hydrogen-electric propulsion systems. It is now preparing for the upcoming first test flight of its ZA600 powertrain, which will use a retrofitted Dornier 228 twin turboprop regional airliner.

First Movements of ZeroAvia's Dornier 228 Aircraft

Following the commercial debut of its initial 10- to 20-seat aircraft in 2025, the company is aiming to get a 40- to 80-seat aircraft into commercial service by 2026, using its 2-megawatt powerplant to convert existing regional airliners such as the ATR42 and the Bombardier Dash 8. That aircraft is expected to offer a range of 1,000 nm, more than triple the range of its first commercial offering.

By 2030, ZeroAvia aims to have a 100- to 200-seat hydrogen airliner enter service, and that aircraft has a planned range of 2,000 nm. Ultimately, ZeroAvia hopes to introduce a hydrogen-powered aircraft with a range of 5,000 nm and more than 200 seats by 2040.

ZeroAvia aims to convert increasingly large airliners to hydrogen propulsion, including potentially the CRJ regional jet. (Image: ZeroAvia)

But ZeroAvia is far from the only company working on hydrogen-powered aircraft. Universal Hydrogen, another California-based aircraft developer, is planning to fly its first hydrogen-powered regional airliner by the end of this year using a hydrogen-fuel-cell-based powertrain housed in one of the nacelles of a De Havilland Dash 8-300 turboprop. In November, Rolls-Royce and EasyJet completed ground tests with a concept demonstrator for a hydrogen propulsion system that could one day be capable of powering narrow-body airliners. Airbus, one of the biggest aircraft manufacturers in the world, is also developing three concepts for possible hydrogen-powered airliners under a project called ZeroE, which the company says could be ready to enter service by 2035.

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