Later, an additional threat to the ozone was hypothesized as a result of the exhaust's nitrogen oxides, a threat that was, in 1974, seemingly validated by MIT. However, while many purely theoretical models were indicating the potential for large ozone losses from SST nitrogen oxides (NOx), other scientists in the paper ""Nitrogen Oxides, Nuclear Weapon Testing, Concorde and Stratospheric Ozone"" turned to historical ozone monitoring and atmospheric nuclear testing to serve as a guide and means of comparison, observing that no detectable ozone loss was evident from approximately 213 megatons of explosive energy being released in 1962, so therefore the equivalent amount of NOx from "1047" Concordes flying "10 hours a day", would likewise, not be unprecedented. In 1981 models and observations were still irreconcilable. More recent computer models in 1995 by David W. Fahey, an atmospheric scientist at the National Oceanic and Atmospheric Administration, and others, suggest that the drop in ozone would be at most, "no more" than 1 to 2% if a fleet of 500 supersonic aircraft was operated. Fahey expressed that this would not be a fatal obstacle for an advanced SST development – while "a big caution flag...should not be a showstopper for advanced SST development" because ""removing the sulfur in the fuel of the [concorde" would essentially eliminate the hypothesized 1–2% ozone-destruction-reaction-pathway.