Sustainable civil aviation is significantly dependent on successfully reducing greenhouse gases produced by commercial aviation. Lighter aircraft, more efficient engines and alternative fuels are the domain of scientists and engineers. It is now time for lawyers to act. The single largest remaining barrier to reducing the environmental impact from aviation is legal; literally those impediments that block “as the crow flies” routings or practices, such as “continuous decent.” If environmental targets are to be met, and every milligram of gases emitted due to human activities is taken into account, it will be obvious that legal initiatives proposed herein must be adopted. This chapter argues that improvements in operations to ensure sustainable flight management should continue and new concepts for the purpose of improving flight management should continuously be developed. In this respect, this chapter addresses relevant provisions of the Chicago Convention, particularly articles 1 and 9, which concern airspace sovereignty and hinder the aviation industry’s objective of achieving sustainable flight management, and provides recommendations to overcome those barriers.