Can aircraft pollutant emissions be reduced by using biofuels? And what influence does an alternative fuel have on the formation of contrails? In mid-January, a joint German Aerospace Center (DLR) and US space agency NASA research project, with the participation of the Max Planck Institute for Chemistry and the Institute for Atmospheric Physics (IPA) of the Johannes Gutenberg University (JGU) in Mainz, addressed these questions. For three weeks, the scientists took off from the US Air Base in Ramstein, in Germany’s Palatinate region, to fly a total of eight test flights at different altitudes and with variable thrust.