In the course of pre-trials within the DLR internal project ‘LOKI’, two DFS controllers tested a validation setup for a digital air traffic controller within an en-route setup. The controllers were able to adjust settings of their radar display and to interact with the digital controller via voice. Hence, no mouse inputs and no navigation within deep menu structures were required. The ATCos could concentrate on the main tasks – controlling air traffic. More precisely, they could highlight aircraft with a specific callsign or within specified flight levels, highlight waypoints, highlight all flights under their control or under control of the digital controller, and delegate the responsibility for a flight between the human and the digital controller. Those speech commands were instructed via a dedicated voice channel that differs from the ATC radio frequency.