With the implementation of the European ATM Master Plan (SESAR, 2012) job requirements for air-traffic controllers (ATCOs) will alter significantly. Especially the introduction of time-based operations is considered to impose large changes in task operations. A controller-in-the-loop simulation study was designed to assess experts' judgments on the main human abilities required for working in time-based arrival scenarios with different levels of assistance by an arrival-management system. Five male controllers (mean age: 32.5 years; mean job experience: 10.8 years) licensed for the simulated sector performed on one baseline scenario and four future scenarios. Gazedata were tracked and questionnaires on situation awareness and workload, as well as a modified Fleishman Job Analysis Survey (F-JAS) were applied. The experts judged the ability to identify problems produced by automation, as well as the ability to stay vigilant as being increasingly required in a highly automated time-based environment. The high number of gaze transitions between aircraft-targets adds objective indication: Under the simulated future conditions ATCOs were hardly able to build up attention guiding expectations which are necessary to keep up with the system-and traffic-parameters. This was also reflected in low situation awareness and high workload ratings.