The global market-based measure adopted in October 2016 by the countries of the International Civil Aviation Organization will limit the net carbon emissions of international flights between participating countries for the years 2021-2035. The limit is initially set at the average of 2019-2020 levels. Provisions in the Carbon Offsetting and Reduction Scheme for International Aviation, or CORSIA, require evaluation of it every 3 years in view of the goals of the Paris Climate Agreement, offering the possibility of tightening the limit in the future. Separately, ICAO is conducting a review of aviation emissions pursuant to the Paris Climate Agreement.

Despite several institutions like the Green Party in Germany, which is suggesting banning CO2 heavy short distance flights, few people expect to drastically reduce air travel. That being said, COVID-19 slashed the number of flights taking place worldwide, but we're already seeing them pick up again as vaccines roll out. Analysts predict that passenger travel will return to 2019 levels by 2024, and cargo flights by mid-2021. While improving fuel consumption and engine efficiency plays an important role in reducing aviation pollution, many politicians and industry leaders hope that hydrogen fuel will save the day, enabling more environmentally-friendly air travel at a reasonable price.

However, various clean fuel alternatives suggested for ground transport aren't practical for airplanes. But hydrogen fuel cell planes are showing promise. It's estimated that hydrogen-powered planes could reduce the climate impact of a flight by 50-75%, compared with a 30-60% change for synthetic fuels. Hydrogen fuel has three times more energy per unit of mass than conventional jet fuel, and over 100 times more than lithium-ion batteries. Hydrogen is available in abundance across the planet, primarily in a compound with oxygen. To produce hydrogen fuel, energy companies use electrolysis to harvest the hydrogen molecules, then store them in pressurized containers until transferring them into a fuel cell which allows the energy to be released as electricity. When the electrolysis is powered by renewable energy sources, the fuel is termed "green hydrogen."