 Aviation traffic volumes have doubled every 15 years since the start of the jet age. Airplane efficiency improvements have nowhere near kept up with this exponential traffic growth. So while the rest of the world is aggressively reducing emissions to avert catastrophic climate change, CO2 from aviation continues to grow. Unlike for cars, batteries are not a viable solution for large commercial airplanes. They're simply too heavy. Hydrogen and so-called sustainable aviation fuels, or SAFs, are the only credible options for new aviation fuels in the foreseeable future. SAFs are synthetic jet fuel in which emissions from burning the hydrocarbon at altitude are offset by carbon capture during the production of the fuel. In this graphic we compare the energy required to produce an equivalent amount of hydrogen and SAF. In order to make this an apples to apples comparison, the hydrogen is green liquid hydrogen produced using water electrolysis, and the SAF is produced using the most mature powered liquid process, capturing an equivalent amount of CO2 to that which is emitted by burning the fuel. The result is that SAF will require about three and a half times more energy to produce, and therefore will cost three and a half times more. While SAFs are convenient near term drop in replacement for fossil derived jet fuel, hydrogen is the only economically viable true zero emission solution for aviation, and it's coming to the skies sooner than you think.