Air traffic control (ATC) displays render a 3D air traffic situation on a 2D planview map. In this projection, altitude is represented only alphanumerically in data tags associated with each aircraft. Controllers must integrate graphical and alphanumeric information channels to represent the true 3D positions of aircraft and search for potential mid-air collisions (conflicts). Palmer, Clausner & Kellman (2008) showed that adding altitude-correlated size and grayscale cues to aircraft icons improved conflict detection performance when observers imagined looking at the ATC scenario from above and the guiding features of size and grayscale were consistent with depth. Here, we show that imagined perspective modulates the effectiveness of these guiding features in ATC displays. The assignment of size and grayscale values to altitudes is the same when observers imagine looking from above and the cues are consistent with depth as it is when observers imagine looking from below and cues are inconsistent with depth. Despite the fact that the ATC displays were identical in these two conditions, observers performed better in the from-above, depth-consistent condition than they did in the from-below, depth-inconsistent condition. We show that improved performance is not due just to depth-consistency, assumed perspective, or larger/darker icons being conceptualized as MORE, but rather to the confluence of all three factors. A second experiment examined the effectiveness of grayscale cues to altitude vs. equiluminant color cues. It was hypothesized that grayscale cues would be more effective for quantitative variations in altitude whereas color cues would be more effective for qualitative variations. We found that equiluminant color cues were indeed more effective at conveying qualitative altitude relations than grayscale cues. We are currently investigating the relative effectiveness of color and grayscale cues for aircraft that quantitatively vary in altitude as when aircraft ascend or descend during flight.