In the air, there were also two competing designs, originating from groups of different backgrounds and needs. The Army Signal Corps, representing military aviators, preferred a solution based on a stream of audio navigation signals, constantly fed into the pilots' ears via a headset. Civilian pilots on the other hand, who were mostly airmail pilots flying cross-country to deliver the mail, felt the audio signals would be annoying and difficult to use over long flights, and preferred a visual solution, with an indicator in the instrument panel.[1]