A possibility to your observation (I have remembered contrails acting pretty much the same as now).
Yes....planes can spray stuff in the air....fire retardant....seeding clouds...etc.
Airlines are not doing this....your observation could be that modern jets have better pressurization systems now, allowing them to cruise at a higher altitude....thus colder temperatures at altitude so the ice particles stay ice longer.
Planes Fly about 30-35,000 ft., and did in the 60s and 70s. I'm a licensed aircraft mechanic. The patents are for an aluminum mixture in the fuel. Also, there were spray nozzles attached to aircraft belonging to Air America, the CIA (Deepstate) airline, which could have sprayed the mixture while in flight. Air temp is relatively the same altitude, and maxes out at 69 degrees Fahrenheit at 37,000 ft.
If no Government would allow this to happen, why would people spend so much time and research and then pay for patents. Here is one such, list of others at bottom.
A possibility to your observation (I have remembered contrails acting pretty much the same as now).
Yes....planes can spray stuff in the air....fire retardant....seeding clouds...etc.
Airlines are not doing this....your observation could be that modern jets have better pressurization systems now, allowing them to cruise at a higher altitude....thus colder temperatures at altitude so the ice particles stay ice longer.
Planes Fly about 30-35,000 ft., and did in the 60s and 70s. I'm a licensed aircraft mechanic. The patents are for an aluminum mixture in the fuel. Also, there were spray nozzles attached to aircraft belonging to Air America, the CIA (Deepstate) airline, which could have sprayed the mixture while in flight. Air temp is relatively the same altitude, and maxes out at 69 degrees Fahrenheit at 37,000 ft.
http://meteorologytraining.tpub.com/14269/css/14269_75.htm
If no Government would allow this to happen, why would people spend so much time and research and then pay for patents. Here is one such, list of others at bottom.
https://patents.google.com/patent/US5003186A/en