The emissions of greenhouse gas from international aviation are growing rapidly. According to figures from the United Nations Framework Convention on Climate Change the emissions from international aviation has increased by 48% in the period 1990-2000. Greenhouse gases from international aviation are not covered by the reduction and limitation commitments under the Kyoto Protocol. However the issue has received still more attention in the ongoing negotiations under the Kyoto Protocol, where especially the quality of data has been addressed. More over it is expected that discussions on allocation will be initiated by 2005. This study includes a review and assessment of the data and methodologies in relation to calculation and reporting of the energy consumption and greenhouse gas emissions from international aviation, as well as issues related to allocation of these emissions to countries. The emphasis is on the assessment of opportunities, advantages and disadvantages of the different methodologies and principles for allocation to the Nordic countries.