The introduction of aviation into the EU-ETS has faced significant opposition from many ICAO member States. Accordingly a global solution through ICAO is in progress. This paper traces the progress of works done by the HGCC in the area of global aviation aspiration goals aiming for the submission to the 38th Session of the ICAO Assembly. Furthermore, devices for calculating the carbon dioxide emissions from flights have been developed by several agencies including international organizations, governments, airlines and nongovernmental organizations. These carbon calculators, however, introduce too many assumptions to simplify the calculation process. This study assesses carbon calculators for aviation emissions and suggests a modified calculation methodology using the pre-existing computer reservation system for better accuracy.