This paper examines the CO2 emission efficiency of airlines in the years 2011 and 2018 by using the Atmosfair Airline Index. This index gives reliable results since it encompasses data from more than 100 airlines and considers important variables in the calculation of CO2 emissions. Firstly, we investigate the regional differences and the effect of the share of government ownership in the CO2 emission efficiency of airlines. These factors have not been taken into account in other studies by using such a comprehensive index. Secondly, by utilizing the Barro and Sala-i Martin model that is commonly used to examine the regional income convergence model in economics, we also check whether there is a convergence in the CO2 emission efficiency of airlines or not. As a result, in terms of efficiency growth, we find that airlines in Europe are more successful compared to airlines from other regions. Furthermore, increases in the share of government ownership in airlines negatively affect the CO2 emission efficiency in Asia, whereas it is insignificant in Europe and America. Moreover, there is no convergence in the CO2 emission efficiency of airlines from all regions. This shows that low-efficient airlines are not catching up with high-efficient airlines. Lastly, we find that charter airlines are more efficient in terms of CO2 emissions.