Air-to-air visibility is discussed with regard to the possibility of using artificial contrails. It is emphasized that although the avoidance of mid-air collisions might be the single most important feature, the use of such contrails may be beneficial in numerous other situations. Experimental evidence obtained in the air, with the assistance of the U.S. Navy Blue Angels, demonstrated that the range of visibility, except for direct head-on courses, is increased from 6-8 miles to 20-24 miles by the use of rather thin white smoke. It is suggested that a smoke of greater density or a different color would increase this range even further.