This news clip that originally aired on December 30th, 1980 cites a study by The Illinois Institute of Natural Resources that determined that the volume of air traffic, and the resulting trials of condensation from the jet engines of the aircraft, significantly affected the natural weather patterns.
Interesting quote from the broadcast by NBC’s Roger O’Neil:
“No one is trying to make clouds now using jet engines. But this study suggests that jet travel is inadvertently making our days more cloudy and some day, weather researchers may be able to use jets on purpose to change our weather.”
SOMETHING TO THINK ABOUT: If in 1980 it was already being admitted on mainstream network news that commercial air traffic was definitely changing the weather patterns inadvertently… imagine what has been done intentionally.
*Link to original video: https://www.youtube.com/watch?v=VuD4yhNVTHE
*Link to The Illinois Institute of Natural Resources study that is referenced in the news report: https://www.isws.illinois.edu/pubdoc/CR/ISWSCR-236.pdf
Many, many thanks to Federal Jack who originally researched and published this information back in September of 2012. Link to original posting: https://www.pakalertpress.com/1980-nbc-news-clip-on-contrails-that-can-change-the-weather-on-purpose/