The prior first phase of this study investigated the effectiveness of new design of flight deck display for required time of arrival operation of NextGen by collecting objective query response data during autopilot flights and subjective data about the perception between display condition and situation awareness level. To evaluate pilots’ mental workload during the operations when they interacted with novel flight deck display design, this second phase provided pilots with simulation flight tasks arriving at four successive waypoints on time in the same display conditions as the first phase and asked them to rate their mental workload ratings. The workload was significantly lower with the High Proximity condition - all space and time data were integrated into a single display and temporal conformance graphics were added removing the need of control display unit - than with the traditional display condition. This result strengthened the implications from the first phase: the close spatial proximity between space and time cues and the support of graphical temporal conformance indicator showed a promise for improved required time of arrival navigation