Quote (ChivasRegal @ Apr 24 2018 08:20pm)
condensation trails last for seconds before disappearing, chemical trails last for hours.....stop being obtuse
Contrails can last for a much longer duration if the air is humid to the point it's near saturation.
On the other hand, dumping chemicals could be done at a lower altitude, without anyone noticing, so why would they choose to make it visible?