Tactical control during a closed-path Continuous Descent Operation stops the aircraft from following its optimized descent. To mitigate tactical control, air traffic controllers apply arbitrary large spacing buffers to account for the unpredictability of the aircraft trajectory from the controller’s point of view. A controller support tool is required for early de-confliction, spacing, and sequencing to facilitate these operations without the need to apply large buffers. The Time-Space Diagram controller support tool was developed to make the constraints and complexity of a Continuous Descent Operation perceptually evident and provide tools and information to the controller to be an active problem solver. This paper addresses the further development and validation of the interface. The concept of Visual Momentum was applied to enhance the efficiency of working the multi-display interface that consists of the Plan View Display and Time-Space Diagram. Direct Manipulation Interfaces were added to enable the controller to plan and implement actions, such as speed and altitude control. A controller-in-the-experiment was setup to validate the interface. In the experiment the subjects used either the Time-Space Diagram support tool or a stack list that provided the required spacing and time to lose or gain as a baseline. Both interfaces enabled the subjects to space the aircraft safely and efficiently. Compared to the baseline, the Time-Space Diagram interface freed time to plan traffic ahead using the Direct Manipulation Interfaces, which according to all subjects worked intuitively. The number of instructions per aircraft was decreased by 25%. Early accurate speed control was applied and use of heading vectors was no longer necessary in most scenarios. As a result aircraft commenced their continuous descent at a higher altitude and greater distance from the runway. The controller workload was significantly reduced and the level of Situational Awareness increased.