The International Civil Aviation Organisation (ICAO) of the United Nations is currently involved in the development and evaluation of options for the control of CO2 emissions from international aviation. This is a difficult process, however, a major problem being the question of how to deal with the aviation of developing countries. Although these countries are not subject to binding emissions targets under the Kyoto Protocol, they are members of ICAO. During the most recent meeting of the UN/ICAO environmental committee, CAEP/5, last January this difficulty was again highlighted. �Several members expressed concerns about the possible negative effects on economic growth in developing States that could result from the implementation of market-based measures (charges, tradable permits). It was felt that further studies should be conducted on the subject, ��. �Concern was also expressed over the effects on competition if only the developed States committed themselves to emissions reduction through an emissions trading regime.� These concerns have been the point of departure for a paper presented by CE Delft at a UNEP/T&E Conference in Paris in April 2002. The paper outlines six systems for controlling greenhouse gas emissions from international aviation, including the use of revenues, that could meet the concerns of both developed and developing states. Preliminary analysis shows as most promising a market-based option limited to all traffic within and between developed countries (annex B countries), regardless of the nationality of the carrier. Such an MBO would neither affect developing countries negatively nor would it lead to unequal competition. After all, the MBO affects everyone equally at the specific partial market. Although such an option would not address all greenhouse-gas emissions by aviation, it would address the greater part. Finally, it would avoid difficult negotiations about transfers of funds between developed and developing countries. This paper has been discussed within the Working Group on Market Based Options of ICAO/CAEP. They decided to include the option mentioned above into their scenario analysis.