Today’s Solutions: December 19, 2025

A little more than two percent of human-caused, global carbon dioxide emissions come from the aviation industry. Like most other modes of transportation, airlines will have to adapt to the emissions-free future, and infrastructure is developing to accommodate the change. European biorefineries are scaling up sustainable aviation fuel production, and major airlines are now starting to buy. 

United Airlines is the first US airline to buy sustainable aviation fuel overseas. 

Sustainable airline fuel take-off

The United Airlines fleet is the biggest in the US and only used .1 percent sustainable airline fuel (SAF) before the Pandemic. As part of its pledge to become carbon neutral by 2050, United Airlines has bought 52.5 million gallons of SAF from European producer Neste to use toward filling every United flight leaving Amsterdam’s Schiphol Airport over the next three years. 

Of course, this small amount of fuel will not be enough to meet United Airlines’ carbon neutrality goals. It will need to scale up and incrementally increase the percentage of SAF fuel it uses on each flight, but first industry standards and laws will have to change. 

Sustainable fuel regulation 

The American Society for Testing and Materials (ASTM) an organization that sets the world standards for aviation fuel, passenger flights cannot legally have more than 50 percent SAF in their tanks. 

“That ceiling of 50% today is arbitrary,” says Lauren Riley, United Airlines’ chief sustainability officer. “The SAF that we use today is a lot more sophisticated, and it works exactly like conventional jet fuel.”

United already proved that planes can run on 100 percent SAF in a test flight from Chicago to Washington DC. As fuel prices lower with tax incentives and the industry becomes more efficient, airline and SAF producers expect the allowable percentage to climb. 

“It’s really just a number that will eventually become 100%,” says Chris Cooper, vice president of Neste. Neste is currently partnering with US airlines United, JetBlue, Alaska, and Delta to run SAF flights out of San Francisco. United Airlines is also committing to other emerging green technologies like jet engines that run on hydrogen-electric fuel and carbon sequestration.

Solutions News Source Print this article
More of Today's Solutions

New method uses sound waves to map soil health, stop famine, and restore farm...

BY THE OPTIMIST DAILY EDITORIAL TEAM Across the world, soil scientists are trading in their shovels for something unexpected: seismic sensors. In a breakthrough ...

Read More

This simple 15-minute mindset exercise can ease anxiety, science shows

BY THE OPTIMIST DAILY EDITORIAL TEAM A growing body of research is revealing how a short, simple activity that is done in just 15 ...

Read More

3 habits of the happiest people

Think of the happiest people you know. Do you find yourself often wondering what they are doing to maintain a general level of joy? ...

Read More

Changemakers of the week: GRuB and SparkNJ

Every day on the Optimist Daily, we report on solutions from around the world. Though we love solutions big and small, the ones that ...

Read More