Less than four months after the Federal Aviation Administration rolled out its 2021 Aviation Climate Action Plan, the agency’s official blueprint for achieving net-zero aviation emissions by 2050 is already starting to look dated. The plan relies overwhelmingly on sustainable aviation fuel (SAF) as the principal pathway for reducing the U.S. aviation sector’s greenhouse gas emissions. It is plainly dismissive of hydrogen, stating: “we do not expect hydrogen-powered aircraft to make a significant contribution toward achieving net-zero aviation emissions by 2050.”