it's like when people show analysis of rain water full of aluminium, barium, strontium and other heavy metals as proof for chemtrails. It's absolutely true that such technique exists (geoengineering) on a military scale but there's no proof that all commercial planes spray everyday everywhere. If the air is polluted, then the cause must be investigated, but until then we cannot conclude it is because of chemtrails. Maybe there are military planes flying everyday with this purpose but I think it is very unlikely that commercial flights do this. A commercial pilot explained when asked about chemtrails, that when they fly over a big ocean like pacific, they carry extra fuel as safety in case they need to change route. Before they land, they usually discard the fuel over the sea because they need to have a certain weight which is exactly calculated for the landing maneuver. Imagine if they had tons of chemicals on board, they would notice it and could not land with an exactly calculated weight.
Now I don't know the truth but I think we have to use logic and don't jump to early conclusion otherwise no one is going to take us seriously because maybe 1 in 100 conspiracy is actually true but then nobody is believing you.
Another interesting thing, I've observed those "chemtrail" are visible most of the time when the weather conditions are changing (ie. rain clouds nearing), but when the weather is stable like in summer there are no trails for weeks.
I too think it's unrealistic that any commercial flight could be part of geoengineering programs for many reasons.