It is included that an increase in the number of stratospheric airliners with present engines will diminish the amount of ozone in the stratosphere and consequently will increase the intensity of ultraviolet light at ground level. The potential harmful biological effects of an increase in the intensity of ultraviolet light at ground level are such that the burden of proof that these consequences can be accepted must lie with those proposing increased use of such aircraft. If additional aircraft are put into service in the stratosphere. one must be prepared for an increase in skin cancer unless appropriate international regulations having the effect of limiting the total emissions of NO, by stratospheric airliners, both subsonic and supersonic, are successfully negotiated and implemented. The seriousness of the potential increase in skin cancer must be judged by the public and their representatives in the light of information such as that summarized...