"Data Comm—a digital, text-based controller-pilot communication system—is critical to many NextGen improvements. With Data Comm, communication becomes a visual task. Although Data Comm brings many advantages, interacting with a visual display may yield an increase in head-down time, particularly for single-pilot operations. This study examined the feasibility of supplementing the visual Data Comm display with an auxiliary synthetic speech presentation. Thirty-two pilots flew two experimental scenarios in a Cessna 172 Flight Training Device. In one scenario, ATC communication was with a text-only Data Comm display; in the other, the text Data Comm display was supplemented with a synthetic speech display annunciating each message (i.e., text+speech). In both scenarios, pilots heard traffic with similar call signs on the party line and received a conditional clearance; however in just one scenario (counter-balanced between communication conditions), pilots received a clearance that was countermanded by a live controller before it was displayed. Results indicated that relative to the text-only display, the text+speech display aided single-pilot performance by reducing head-down time; and it may have prevented participants from acting prematurely on the conditional clearance. Supplementing text Data Comm with speech did not introduce additional complications: participants were neither more likely to erroneously respond to similar call signs, nor to ignore a live ATC voice countermand. The results suggest that the text+speech display did not hinder single-pilot performance and offered some benefits compared to the text-only display."--U.S. Department of Transportation website