You have the following statements: <QUOTE> Scientific studies during the early 1970s showed that SSts flying through the stratosphere released nitrogen oxides in exhaust gases.
Ironically, nitrogen compounds that help produce ozone in the troposphere are part of a chemical process that destroys ozone in the stratosphere. Although the threat to the ozone layer was a consideration in whether or not SSTs should be manufactured, the project eventually was dropped because the production of SSTs became too costly. <END QUOTE> The presence of oxides of nitrogen in the exhaust is inconsequential. What is important is that there was humidity in the exhaust, that converted the oxides of nitrogen to something that *cannot* produce ozone when expsoed to visible light. Water is not found in quantity at high altitudes... especially in a molecular vapor.
