Trajectory based operations will be an important concept in tomorrow’s Air Traffic Management. The concept is a complex puzzle that includes both strategical and tactical aspects to achieve increased predictability and efficiency. However, research related to trajectory based operations has been focusing on strategical or technical perspectives, thus not addressing how it effects, and is affected by, the air traffic controllers work situation. In this study, we conducted real-time simulations with air traffic controllers to explore how the introduction of a tactical trajectory management tool affects the controllers’ work strategies for conflict resolution. A tool for tactical trajectory management was developed and integrated in an Air Traffic Control simulator, and tested with realistic traffic scenarios. The results showed that by using tactical trajectory management, it was possible to reduce the need for the air traffic controllers to monitor implemented conflict solutions. The tool was incorporated by the controllers in their current work strategies for conflict resolution rather than changing their strategies. However, it also highlighted the need for more advanced support tools for trajectory management in solving vertical conflicts and using temporal constraints.