A flexible interface for prescribing complex and diverse aircraft trajectories called GenProf was developed and tested on the Center TRACON Automation System (CTAS) software research platform. This interface models various pilot procedures, supports common flight constraints imposed by air traffic control, and allows the building of trajectories in accordance with new flight procedures. In addition to serving trajectory generation for air traffic management decision support tools and concepts, the GenProf methodology has enabled a variety of research and validation tasks to be performed. This paper describes the interface and details these applications.