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As a climate reporter, I sometimes hesitate to admit this, but I feel it’s time that I came clean on something … I love flying. It’s not even just about traveling and seeing new places: I truly enjoy the process, from sitting in an airport terminal to sliding into a window seat. I even appreciate the elegance of a smooth trip through airport security. Unhinged, I know. 

My love affair with flying and my work covering climate change feel at odds because aviation makes up about 3% of the world’s greenhouse-gas emissions—almost a gigaton in 2019. Airline traffic could more than double from today’s levels by 2050. 

And we really don’t know what we’re going to do about it.

Aviation is one of those notorious “hard-to-decarbonize” sectors, where the technical challenge of cutting emissions is especially steep. Fuels for planes need to be especially light and compact, so planes can make it into the sky and still have room for people or cargo. 

The industry has some ideas for technologies that could cut emissions, and some are even starting to make it to test flights. Last week, a startup completed a test flight of the largest plane yet that was powered by hydrogen. So for the newsletter this week, let’s take a look at the technologies that could transform aviation, how long they might take to make an impact, and where that test flight fits in. 

There are a few potential technologies on the table that could help cut emissions from aviation (and help relieve my flying guilt).

Sustainable aviation fuels, or SAFs, are drop-in replacements to jet fuel made from non-fossil sources. There’s a pretty wide range of SAFs out there, including those made with waste oils and fats, those derived from biomass, and fully synthetic e-fuels.&n...