The FLAIR team performed a week-long measurement campaign over the waters of the Kategatt, the strait linking the Nord Sea with the Baltic Sea. In collaboration with Explicit, a Danish company specialized in airborne pollutant detection, and Charlie9, a Helicopter company based near Copenhagen, more than 120 ships could be targeted, and their exhaust fumes analyzed. The FLAIR system has been tuned to target methane, a potent greenhouse gas, with absorption lines matching the