Air Travel

These Major Airlines Just Flew Planes Powered Entirely by Sustainable Aviation Fuel—So, What's Next?

Flight engines are revving up with cleaner alternatives.
Airplanes taxiing on runway at sunset
Colin Anderson Productions pty ltd/Getty Images

Air travel contributes to 2.5 percent of our global carbon emissions, often getting named as one of the biggest contributors to climate change. So it’s no surprise that airlines are all upping their sustainability efforts, especially in the race to find jet fuel alternatives in the form of sustainable aviation fuel (SAF).

Three weeks ago, Emirates successfully completed a demo flight on an A380 from Dubai International Airport, with one of its four engines using 100 percent SAF. “This demonstrated SAF’s potential as a viable alternative that matches jet fuel’s technical and chemical requirements while being more sustainable,” a spokesperson for the Dubai-based carrier tells Condé Nast Traveler of the November 22 milestone.

Less than a week later, Virgin Atlantic also grabbed headlines, completing the first trans-Atlantic Ocean flight from London Heathrow to New York City’s John F. Kennedy, on a Boeing 787 running on Rolls-Royce Trent 1000 engines fueled completely by 100 percent SAF. But there's more to celebrate than just the flight distance. What made this trip—dubbed Flight 100—so notable was that it received a special permit from the UK to go beyond the current global 50 percent SAF limit on commercial flights to go all in on the alternative. “Flight 100 proves that SAF is a safe drop-in replacement for fossil-derived jet fuel and the only mid-term viable solution for decarbonizing long-haul aviation,” the UK-based carrier’s spokesperson says.

It can be tough to wrap your head around the technicalities, so we broke down what this means for the future of travel ahead.

What is SAF made of?

A United spokesperson explains that the fuel alternative can be made from all sorts of renewable sources, including ethanol, algae, municipal waste, as well as captured and repurposed carbon. “In its final form, SAF is almost chemically identical to normal jet fuel, and meets the same strict industry standards for conventional jet fuel, but can reduce a plane’s emissions by up to 85 percent,” the Chicago-based carrier says.

For example, Flight 100 used a “unique dual blend," according to the airline's spokeperson. It contained 88 percent AirBP-supplied Hydroprocessed Esters and Fatty Acids (HEFA) made of waste fats, and 12 percent Virent-provided Synthetic Aromatic Kerosene (SAK), which is made from plant sugars. Fully 100 percent SAF blends all require SAK “to give the fuel the required aromatics for engine function,” the airline explains.

Will fliers notice the difference?

The two airlines say that, for consumers, the SAF-powered flight experience will be exactly the same as ones powered by traditional fuel. Where travelers could see a difference is on the price tag. After all, right now there isn’t the supply needed to fuel planes on a large scale, so the low supply means higher prices for the airlines.

“In the short term, we don’t foresee any impact to the pricing for travelers and we can also cannot speculate on future pricing as energy prices in general are volatile and affected by numerous factors and SAF is very much a frontier industry,” the Emirates rep says.

The obstacles of fully sustainable jet fuel use

As with any massive, industry-wide innovation, there are challenges ahead. The Virgin Atlantic spokesperson says in the end, it’s up to advancing policy and investment in order to pull down the production costs. “This is why we are pressing for urgent action from [the] government to de-risk SAF investment,” they note.

Right now, SAF is used in less than 0.1 percent of global jet fuel volumes. “Flight 100 proves that the challenge of scaling up production is one of policy and investment, and industry and government must move quickly to create a thriving UK SAF industry,” Virgin Atlantic’s spokesperson says.

The future (and recent past) of sustainable jet fuel

Both successful missions show that going beyond the current limits is feasible—and necessary. “This achievement contributes to the growing body of research on the beneficial impact of 100 percent SAF on aircraft performance, setting the stage for future standardization, qualification, and adoption while supporting global efforts to combat climate change and promote eco-friendly air travel practices,” the Emirates rep says, noting it could be used in greater concentrations and “potentially in all four engines.”

While last month’s flights put alternative aviation fuel back in the news, United actually successfully completed its first 100 percent SAF flight back in December 2021. Taking off from Chicago O’Hare and arriving in Washington, D.C.’s Reagan National in a Boeing 737 Max 8, the landmark flight used 500 gallons of pure SAF in one of its two engines. The Chicago-based operator is also part of Boeing’s EcoDemonstrator program, which has tested 100 percent SAF in both engines in recent months as well.

United has also been rolling SAF into its operations in San Francisco, Los Angeles, London Heathrow, and Amsterdam, setting it on track to increase use this year two-fold compared to last year and five times more than in 2019.

Which airlines are investing in sustainable fuel?

Every airline has been taking their own approach to scaling up. Domestically, last summer, American Airlines committed to purchasing 500 million gallons of SAF over five years from Gevo and Delta currently has contracts for half of its goal to run on 10 percent SAF by the end of 2030.

Across the ocean, Lufthansa Group has invested $250 million into obtaining SAF, as well as “collaborating in numerous projects worldwide to increase SAF’s availability," including focusing on forward-looking methods, including power-to-liquid (PtL) and sun-to-liquid (StL) technologies.

KLM has been working with engine manufacturer CFM International and fuel producer Neste (which creates its SAF from used frying oil), and earlier this year, they conducted a test running an CFM56-7B engine on 100 percent SAF, confirming that it “can be used safely,” the airline tells CNT. "This test is a small, but significant step towards making the airline industry more sustainable.” Together with partner Air France, the Air France-KLM Group was the largest user of SAF in the world in 2022, accounting for 17 percent of the total production.

On the manufacturing front, Boeing and Airbus have also committed to designing aircraft that run on 100 percent SAF by 2030. “Sustainable aviation fuel is the best tool we have to decarbonize airplanes,” United’s rep says. Emirates’ spokesperson adds that “recognizing its importance as a vital step towards greener aviation and achieving net-zero carbon emissions in the industry by 2050” explaining that “as SAF becomes increasingly available and embraced, travelers can expect a rising number of flights powered by this sustainable alternative.”