There would thus appear to be an overwhelming case for some form of MBM to complement the operational, technical and infrastructure elements in a ‘basket’ of emissions mitigation measures. There will of course be some variance in the extent of the MBM requirement from airline to airline and state to state. In this context, the widely varying positions by major aviation parties and the divergence on treaty principles (the UNFCCC’s CBDR&RC versus ICAO’s equal treatment) do not bode well for a global agreement on MBMs.