Application of commercial aircraft based observations of greenhouse gases to carbon cycle science Robust and sustained observations of atmospheric greenhouse gases like CO2 and CH4 are of great importance in order to understand the current state of the global carbon cycle and for the reliable prediction of climate change scenarios. The current observational network is largely a combination of ground based stations satellite instruments and research aircraft. In recent years a new concept has emerged in the field of global atmospheric monitoring that uses the existing commercial aviation infrastructure and deploys hi tech instruments onboard commercial airliners. These instruments make highly precise in situ observations of atmospheric species at a high spatial and temporal resolution while the aircraft performs its intended task of flying people from one part of the globe to the other. Vertical profiles are measured near airports and cruise level data are obtained in the UTLS (Upper Troposphere Lower Stratosphere) region thus providing a rich and extensive dataset for studying the chemical and physical processes in the atmosphere.