The transportation sector is the most significant contributor to US greenhouse gas (GHG) emissions, accounting for 27% of the total. However, amid changing popular opinion and government regulations, the airline industry is trying to clean up its act. Some airlines claim sustainable aviation fuel (SAF) is the key to carbon-neutral flight. But is it? This article explores how providers make SAF, whether it works, and what airlines actually mean when they claim to be "carbon neutral."