A bottleneck of (future) multiple remote tower operations (MRTO) is for controllers to monitor traffic movements at two airports (or more) in real-time, at the same time. To address this, we propose an autonomous agent (digital colleague), the DiTA Digital Tower Assistant. The key issue addressed by the DiTA concept is simultaneous movements on the two airports. We present results from the first stages of concept design and evaluation of DiTA. We conducted two workshops with three fully licensed air traffic controllers. During the workshops the controllers evaluated the DiTA concept of operations through scenario walk-throughs using printed airspace maps. The outcome of the workshop series was a tentative concept of DiTA operations and key concerns for one MRTO scenario. We present and discuss the emerging picture of common concerns and views on acceptable concept of operations as the workshops progressed. We conclude that it is is vital that operators can place the right level of trust in autonomous system competence, especially when they manage safety critical movements. To achieve this, DiTA competence is a key concern. The build-up of operator trust and competence to assess DiTA comptence (re-skilling) could both rely on automation transparency and a stepwise introduction of the concept in operations.