Unlike aircraft design, the commercial aviation industry’s aspirational pledges for slashing its climate impact by mid-century depend on nearly everything going right.

Last month, the International Air Transport Association (IATA), whose 290 member airlines include almost every major carrier and move more than 80% of the world’s flyers, introduced a non-binding net-zero pledge for cutting emissions. And tomorrow, Britain plans to announce a new international aviation emissions coalition at the United Nations’ climate summit, COP26, underway in Glasgow, according to a UK government spokesman.

Commercial aviation accounts for about 3.5% of man-made climate change, according to the scientific journal Atmospheric Environment. (Other researchers put the number at 5%.) The industry, though, is running out of time to help hold global warming to a 1.5 degree Celsius (2.7 degrees F) increase above pre-industrial levels—the 2015 Paris Agreement’s target, according to a paper published by Nature Communications in June.

Carbon emissions are just one part of the industry’s contribution to climate change; nitrogen oxides, which form inside jet engines, and contrail cirrus clouds, which trap heat similar to greenhouse gases, are also major contributors. But just getting to net-zero carbon emissions will require huge investments, myriad technological leaps, and concerted action from thousands of companies, organizations and governments, with plenty of conflicting incentives among them.

IATA’s net-zero pledge came with a rough roadmap for cutting emissions—and an estimated $1.6 trillion price tag: 63% of the emissions reductions would come from sustainable aviation fuels, known as SAF, 19% from carbon capture and offsets, 13% from breakthrough airplane technologies, such as hydrogen propulsion, and 3% from more efficient operations and infrastructure. (Flying less was not on the list.) 

A lot of these reductions depend on technological breakthroughs that the industry may not be able to deliver—at least, not in that time frame. While every new jetliner is more fuel efficient and creates fewer emissions than older models, those emission reductions are being outpaced by the commercial aviation industry’s growth, and the industry must do more if it is going to cut emissions, Boeing’s director of environmental sustainability Sean Newsum said. “We are committed to developing more sustainable projects,” he said.

Boeing’s priority is developing a plane that can fly on 100% SAF, such as biofuels, by 2030. The company is also working on hydrogen propulsion, but company officials think it likely won’t be viable before 2050. 

Rival airplane maker Airbus is betting on hydrogen combustion and fuel cells, and hopes to offer a zero-emission short-haul airliner by 2035. The European aerospace giant is also working on 100% SAF. Neither company will say how much it invests in R&D for sustainable technologies.  

“It’s not good enough that we get incremental change in efficiency with the aircraft,” IATA’s head Willie Walsh said during the association’s October meeting. “To get to net zero we’re going to need a fundamental change.”

Several startup companies are developing all-electric and electric hybrid small commercial planes. Alaska Airlines and startup ZeroAvia are developing hydrogen-fuel cell conversion kits for the 76-seat turboprop De Havilland Q400, a mainstay of Seattle-based airlines’ subsidiary Horizon Air. ZeroAvia also has said its 19-passenger hydrogen-electric airplane in development can start commercial flights as soon as 2024.

The aerospace industry is quickly running out of time to become climate neutral by 2050. At the current pace of efficiency gains, the industry has little chance of curbing its climate impacts in time, according to a team of researchers with ECATS (Environmentally Compatible Air Transport System), who wrote the paper in Nature Communications.

With concerted action, the industry can possibly make the changes it needs to, said Joris Melkert, one of the researchers on the team and an aerospace professor at Delft University of Technology. But decisions made in the next couple years are critical to getting there, he said. For breakthrough airplane technology to make a meaningful contribution, airplane manufacturers  “probably need to be at least quite a way into detailed design,” Melkert said. Also, IATA’s goal is to be carbon neutral, not climate neutral, he noted.

Sustainable aviation fuels are widely seen as the best way to drastically reduce carbon emissions, but ramping up the supply chain for these fuels may also present a challenge. Commercial aviation has spent more than a decade developing them for widespread use, and current jetliners can use up to 50% SAF, but sustainable aviation fuels make up less than 0.1% of global jet fuel supply.

Using a back-of-the-envelope estimate, building a global supply chain to meet IATA’s 10% SAF in 2030 target could require $117 billion to $350 billion in investments, said Tom Berg, policy and sustainability manager at SAF producer SkyNRG.

The global supply chain likely will consist of several regional supply chains making SAF with regionally-sourced biomass material, such as forestry waste in the Pacific Northwest, and even turning carbon dioxide into sustainable fuel. 

Then there is the price. SAF today typically costs four times as much as jet fuel. IATA, Boeing and others say increasing production will lower SAF’s price, and that governments need to subsidize sustainable fuels to get the cost close to conventional fuel.

Paying more for SAF is virtually a nonstarter for the fastest growing airline segment, low cost carriers—airlines who depend on cheap fares to drive traffic, especially leisure travel, Mann said.

Airlines typically pass fuel prices on to customers, but many passengers on low-cost carriers might not be able to afford higher fares.

“If a ticket is $30, and it goes up $30 per trip because of higher fuel prices, many of their travelers will be priced out,” he said. “The same $30 increase doesn’t matter as much for a passenger on a legacy airline who already was paying $300 or more for a ticket.”

Despite all the challenges, aerospace professor Melkert remains hopeful that the industry can make the big changes required in time.

“I’m quite optimistic that if we really feel the pressure, we can make it happen,” he said.

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