How innocent is the white smoke that planes leave behind as they move forward? Some theories say that this gas is much more dangerous than ordinary fuel waste. Are some high minds mixing active ingredients into the fuels of some planes to keep the human population or intelligence to a minimum? When and where the planes will pass is predetermined and every route is clear unless there is an extreme situation. Perhaps this is the easiest way to spread an airborne active substance. Which region do you want to spread? How often and how intensely do you want to spread it? It doesn't seem like very advanced technology is needed for such a purpose. What if a plan that will have an effect in 100 years has been implemented for the last 50 years? What would the world look like 50 years from now?