As the Editor states does this manuscript describe application of long-path absorption spectroscopy to detection of gas leak plumes. The technique uses an unmanned aerial vehicle (UAV) carrying a retroreflector as the endpoint of the absorption path, which allows for rapid discovery of plume location and quantification of plume cross section for emissions rate determination. The technique works at a safe standoff distance and through the use of the UAV doesn't need two fixed end locations. It would be of interest to many seeking to find and quantify gas leaks, which is important for safety and minimizing greenhouse gas and reactive gas emissions.