What is Sustainable Aviation Fuel? How Travelers Can Make A Difference With Every Flight
This is Part 2 in our series on how to book more sustainable flights by using a new platform called BookBetter. Today, it’s all about Sustainable Aviation Fuel – what it is, how much of an impact it actually has, and the easiest way you can buy it. (Be sure to check out Part 1, about contrails and the 3 other factors that determine each flight’s climate impact.)
What is Sustainable Aviation Fuel?
Sustainable Aviation Fuel (SAF) is actually a pretty simple concept: It’s jet fuel made out of anything other than fossil fuels. Sounds too good to be true? Well, luckily it’s not.
The most common kind of SAF right now is made from used cooking oil, and it reduces the greenhouse gas emissions of a flight by 80%.
(EIGHTY PERCENT!!! How cool is that!?)
Another kind of SAF is made with waste from farms or forests (think corn husks or undergrowth cleared from the woods). And then there’s e-SAF, which is made from the carbon that’s captured from the air, and sounds even more like science fiction, but is also real.
BookBetter calls e-SAF a “next generation fuel” that will cut jet fuel emissions by 95%. (That’s basically down to zero.)
Fun but not the point:
If you’re interested in real technologies that are so exciting they sound like science fiction and remove CO2 from the air, check out this short video we made about one simple kind of carbon removal:
Zero emission flights??
No, we’re not quite talking about zero-emission flights, yet, even at 95% reduction. That’s mostly because fuel is only part of the equation that defines the climate impact of a flight.
To put it simply: When all other factors are the same (same flight route, same jet engine) a flight’s total climate impact is a combination of greenhouse gas emissions (from burning fuel, and whether it’s SAF or fossil fuel) and “non-CO2” factors (mostly the climate impact of jet contrails).
So even with next-generation SAF, there would still be the contrail factor, which can contribute about half of the total climate impact of a flight. (Seriously, I really recommend you read my first post about contrails and why different flights have different climate impacts, so I’m linking it again. It’ll make all of this so much clearer.)
But the other half of the emissions equation is basically solved by SAF, which I find just wildly inspiring!
Side note – how do you say “SAF”?
Before we go any further, it’s pronounced “SAF” like NASA, like S.A.F. like the CIA. That way when you start leaving voicemails for Congress about passing the SAF bills on their desks, they’ll know you know what you’re talking about.
How can you make sure your flight burns SAF?
This is actually the easiest win of this whole topic: Just book your flights with BookBetter! When you do, you can choose how much SAF you want to buy during the booking process (no extra steps or second websites).
BookBetter
And by “choose,” I mean anywhere from 1% of the fuel for your flight, which will cost you about the same as a cup of coffee or less, to 100% of the fuel, which costs more like the price of checking a bag or upgrading from basic to normal economy.
Will the SAF you buy go into the plane you fly on?
Not necessarily. But the SAF you buy through BookBetter goes into the jet fuel supply at airports, and that fuel is all part of the same bucket. (And you get a certificate showing that your purchase actually happened, and actually increased the SAF supply in those airport fuel buckets.)
So right now, at least you know someone is flying more sustainably because of you. And that absolutely makes a difference.
Example for the nerds:
On my recent flight from Mexico City to Boston, I used BookBetter and chose 100% SAF.
Two days after my flight, I had this in my inbox, with a link to the international organization that keeps track of SAF purchases:
The document shows exactly how much I reduced the climate impact of my flight (80%), and confirmed that the SAF I bought was HEFA (the kind made of used cooking oil, and by far the most common kind of SAF) and was made by a Finnish company called Neste (the biggest name in SAF production).
With that “retirement ID,” I could even look up the verification on the third-party SAF registry that proves my BookBetter flight actually increased production of sustainable jet fuel, and feel a little warmer and fuzzier inside.
Bottom Line:
So let’s put it this way: When everyone who buys a flight opts for SAF, then you’ll know you’re flying with SAF. Right now, that isn’t possible because not enough of it is being made. But we can help push for more by buying more. (That’s capitalism, baby.)
The Best Part:
Even choosing 1% SAF matters! It’s a vote, it’s a signal to the market, and it’s another tally mark in the “look how many users we have who care about this” column for BookBetter to show potential investors and, who knows, even governments. (More on that concept below.)
Science Talk: How does SAF actually reduce emissions?
After all, burning SAF is still burning jet fuel, right?
What makes SAF different from regular fossil jet fuel is something called “lifecycle emissions.” It’s all about the ingredients in the recipe used to make the fuel.
Since we’re on the topic of food, Louis Lammertyn, one of the co-founders of BookBetter, sent me an excellent food analogy to explain SAF:
“When we eat a sandwich, our body uses the energy and we exhale CO₂. This CO₂ is not problematic because it comes from natural sources and returns to the natural carbon cycle.”
Louis, BookBetter co-founder
The same principle applies to SAF. The carbon released when we burn SAF is from biogenic or recycled sources (forest undergrowth or used cooking oil), NOT from newly extracted fossil fuels.
So yes, burning SAF for your flight still releases CO2, but it’s not new CO2. It’s already part of the natural carbon cycle of trees growing and decomposing, to put it simply.
Whereas traditional fossil fuels – whether it’s natural gas for your kitchen stove, diesel / gasoline in your car, or jet fuel for your flight – are adding new carbon to the atmosphere.
Great, you say, but…
Is this big enough to matter?
Yes, of course, sustainable aviation fuel is far from being mainstream, but it is growing fast. Shockingly fast, in fact.
The Good News on SAF
Use of sustainable aviation fuel use has scaled 100x in less than a decade! (That’s faster than the early stages of wind and solar growth.)
Sure, the starting point was very small. In 2019, there were about 20,000 tonnes of SAF in circulation.
In 2025, SAF output reached 1.9 million tonnes. That’s basically double the 1 million tonnes produced in 2024. And it’s a 100x growth rate from 2019 to 2025.
So sure, if you want to cling to the negative-sounding stats, SAF was still “only” 0.6% of all the jet fuel used in 2025. (With Europe leading the pack – they beat their 2% SAF goal last year. Good job, my friends.)
And .6% is a lot higher than the last stat I heard at a sustainable travel conference a couple of years ago! (It was around .1%.)
In 2026, SAF is expected to be .8% of global jet fuel consumption!
I find it profoundly inspiring that this has actually been going in a positive direction. But the reality is that the growth rate has slowed. Which means…
All aboard the SAF train!
Great, you might think, as you dust off your hands and close your computer, SAF has grown 100x. I don’t need to worry about it (or spend money on it).
But WAIT! DON’T GO YET!
All the growth in Sustainable Aviation Fuel is thanks to lots of factors, all working together.
It’s the laws requiring more SAF use.
It’s investments from airports, and aircraft makers like Airbus and Boeing.
It’s airlines like United and Air France-KLM buying SAF today, and making plans to buy more tomorrow.
(Air France-KLM is the best airline in the world for SAF use, according to this useful airline ranking. United is second (and was the first US airline to regularly use it, starting back in 2016). Southwest, JetBlue, and Delta are also in the top ten, so keep that in mind when choosing an airline. And remember, it’s not just people who fly; stuff flies, too. DHL is number 7, whereas FedEx is way down at 30.)
And it’s also PEOPLE asking for SAF through their votes and purchases.
That’s where BookBetter is doing such an amazing job. They’ve created a real option for travelers like you and me to show that we actually care about this technology.
They’ve made it way easier than before to vote with your wallet and be one of those people asking for SAF. You literally just book your flights with them, choose the level of SAF that you feel comfortable paying for, and that’s it. Your vote is counted.
Speaking of Trains…
It should go without saying, but yes, even with SAF, train travel is more sustainable than air travel. But it’s not always possible, or realistic.
And BookBetter is planning expand to offer train bookings, as well, so that you can skip the travel carbon calculator and see how much climate impact you can actually save for each trip on the same platform where you book your tickets.
Right now, the site will suggest you consider booking a train trip for shorter trips where that’s an option:
[ Related: Check out my guide comparing the best websites for booking trains in Europe, including Rail Europe, which I like because it gives climate impact information.]
Final Inspiration from a SAF expert:
Do our choices really matter?
On an excellent webinar that BookBetter hosted about sustainable flying, Daniel Bloch, an international expert on sustainable aviation fuel, gave the best possible answer to this question:
“If everyone adopted a mentality of I’m not particularly important, we wouldn’t have a particularly effective democracy.”
Daniel, Sustainable Aviation Fuel expert
I think we should all write that on our bathroom mirrors so it’ll be the first thing we read in the mornings. We absolutely need that reminder for whenever we start to wonder whether our purchases or our votes really matter.
Of course they matter. Our purchases and votes are the only things that matter. The growth of SAF over just a few short years is proof of that.
The only people who want you to believe they don’t matter are the corporations who benefit from us feeling depressed and demotivated and not bothering to change the world. (And the people who are too jaded and afraid to try to change the world, but that’s another story.)
What to do next:
If you want to learn more, you’re in luck, because I’ve got a whole web of articles on sustainable travel tips. I think they’re all actionable, easy to read and pretty entertaining, but I’m open to feedback! What do you think? What would you like to see more of?
- If you still haven’t clicked, I’ll put it here one more time: My post on jet contrail climate impact and choosing more sustainable flights.
- 10 sustainable tips that are more useful than “Don’t Fly”
- The best travel carbon calculators for every kind of trip (I tested them all)
- Why we need more carbon removal in the travel industry (and how you can help!)
- Hey, what do we think about offsetting flight emissions?
And keep in touch!
Ready to travel?
Or maybe this was already more than enough info, but all this flight talk has you ready to book a trip? Yeah, I get it. Next time you book a flight, make a difference by booking through BookBetter! (And support Tilted Map by using my discount code below.)
BookBetter
- My blog post with all my pro tips for using BookBetter is coming soon!
Sustainable Destination Inspiration:
If you want to read about trips that are designed with sustainability in mind, here are some of my favorites:
- The e-bike trips I host in Italy – you can even join us this year! (There’s even a preview video.)
- A unique experience with an indigenous tribe in China (there’s a video for that one, too).
- The best organic-only wine tastings in Napa Valley
