Environmental effects of an aircraft at cruise: An update

The status of the calculations of ozone change due to high altitude aircraft is critically reviewed and important areas of uncertainty identified. Laboratory determinations of chemical reaction rates and modeling refinements show that the effect of cruise altitude emissions on stratospheric ozone has changed from one of ozone decrease to one of slight increase. It is concluded that the uncertainties in the present understanding of the effects of high altitude aircraft are such as to warrant continued studies.