Significant fuel and emissions savings can be realized by an efficient air traffic management system. Throughout the recent years, vertical flight efficiency has been identified as an improvement area. Continuous climb and descent operations are important elements of the on-going air navigation system modernization efforts. This paper expands the joint work by FAA and EUROCONTROL with a view to develop a harmonized understanding and methodology to measure and assess operational air traffic management performance. The work is conducted as an empirical study under the umbrella of the biennial regional US/Europe operational comparison report. Next to updating the assessment of the descent phase, the 2018 edition will include and assess the climb phase. The overall comparison is augmented with case studies for specific airports where a balance between operational constraints and improved efficiency needs to be struck. While initial results point at a higher benefit potential for the descent phase, addressing both phases of flight is essential to provide policy makers and air traffic management decision makers with performance results to further prioritize implementation options and changes to the operational concept.