The ICAO High Level Group in International Aviation and Climate Change, established last November to resolve political questions surrounding a global market based measure for international aviation emissions, also needs to agree an ICAO position on the geographic scope of any national or regional schemes such as the EU ETS. The three alternatives being considered are based on departing flights, nationality of carrier or a country’s airspace. Suggestions that an airspace approach would be appropriate are unrealistic and can't be serious. ICAO already recognised 5 years ago that the airspace option was impractical. These talks require a more responsible and disinterested approach and here we explain why.