This paper studies the determinants of vertical efficiency of aircraft approach at the lower airspace, particularly those linked to air traffic control. First, we specify two vertical efficiency metrics and apply them to data from Frankfurt airport. Accordingly, 10.6% of approaches fly vertically efficiently without leveling off and 35% in the optimal approach window. Over 60% of the level-off time is flown below 1750 m, an area particularly critical concerning environmental influences. Second, we run MM and Tobit regressions to identify the determinants of vertical efficiency. We find that variables linked to air traffic control, such as approach runways and routes, are significantly associated with both metrics. This is evidence of the impact of air traffic control on vertical efficiency. We conclude that air traffic management may be able to contribute to more efficient flight procedures and reduce the environmental impact without compromising flight safety. The metrics can also be used to compare approaches to different airports concisely.