Despite pilots’ training and technology aids, mid-air collisions can occur and do occur, especially near airfields and in non-controlled airspaces where different kinds of aircraft fly. Technology typically helps pilots in the form of a flat display in the cockpit that shows nearby air traffic. New airliners are now fitted with see-through displays (HUD) to present information right in front of the pilot, and modern military fighters mount that kind of displays in the pilot’s helmet to help them no matter what direction they are looking in. This technology, however, could reach light and sport aviation in the next years thanks to new light and affordable Augmented Reality (AR) glasses, such as the ones targeting applications in urban mobility. Looking ahead to that moment, in this work we rely on Virtual Reality (VR) -in particular, Cardboard VR- to prototype and test different AR interfaces for air traffic alert. Firstly, we proposed and tested four different head-mounted display (HMD) AR interfaces with four pilots in our own VR aircraft-proximity simulator. Then, the two best-scored interfaces were selected for a second evaluation, and they were compared against another proposal (Circular HUD by Alce et al.) and a fixed-mounted (FM) conventional HUD radar (FMHUD Radar), tested by four additional pilots. Overall, pilots showed preference for our AR proposals. Interestingly, pilots with more experience preferred the more conventional, radar-like designs, while those with less flight hours were more open to a different, novel design (HMD 3D Arrow).