The best I can give you on the subject is my conclusions from a lifetime of experience with airplanes.
Jets had one big stealth problem: vapor trails. You can't sneak over a country leaving a big old trail behind you. Not only that but the trail made an excellent sighting mechanism for a missile launcher. So the main thrust in one area of research was getting rid of the evidence the jet left behind. They certainly were not trying to leave huge trails like you see in the above picture. The only solution anyone could come up with because attempting to eliminate the trail all together caused the engine to stall out and that resulted in a large splatter, was to cause the trails to dissolve as fast as possible. I think you can conclude those trails in the picture are not dissolving very fast.
So, what are they?
My favorite weatherperson was waxing eloquently about the gorgeous South Florida weather and the fact that there was not a single cloud in the turquoise sky and clicked on the ground radar, not the Doppler, to show us the beautiful image of a completely obscured Palm Beach County. Looking down at his monitor and realizing he was looking a bit like an idiot he exclaimed, "Oh those aren't clouds. The military is conducting spraying exercises over the area today. That is metallic residue in the air reflecting off the radar" and got the 'oh, crap did I just say that out loud' look on his face. Oops, someone let the cat out the bag big time.
So, you might conclude these are NOT vapor trails. But, what is their purpose?
If you had seen the actual radar image you could have come up with one quick purpose. Any area using ground radar would be completely unable to see an entire fleet of air craft arriving after those Chem Trails bleed out into a solid mesh over the area. They would be blind, particularly at night.
But the problem with that is few countries use the old ground radar system for anything other than weather.
Well, you might want to download the study at this link. Or just read it on line because I had trouble getting to the actual download link and gave up. But basically one theory is they are spreading metals in the atmosphere to try and stop the warming of the earth.
That's a lofty ideal, flawed science and I don't think it's right. First of all, I have watched carefully where the chem trails are being sprayed in my area and they follow a definite pattern. It is a pattern something else follows.
Almost 27 years ago, I took to raising orchids. I bought commercial sun screen from a commercial nursery supply which they actually will cut and stitch it to your dimensions for your shade house. Thought you might like to know that. It comes in various thicknesses dependent on how much sun you want to block. Phalaenopsis or Moth Orchids are easy to grow and profitable so they were my focus and they also require the highest level of sun block. At the end of 6 months, my orchids were burning and a month later my sun screen began to disintegrate.
This stuff is not cheap so I was bit peeved, cut a piece of it and went back to the nursery supply. They packed it up and sent it to the manufacturer who called me within the week and asked where exactly I had their sun screen installed. Well, in the backyard was the answer. The gentleman suggested I not go outside, except at night. This screen had received the equivalent of 10 years of solar radiation in 6 months, something which should be impossible.
Knowing that, I began tapping every source I had because the internet didn't exist at that point and there was no Google. Actually, there were no PC's except for little Commodore 64's. Finally I got a totally off the record answer. It seems there was a huge 5 to 10 mile hole in the ozone that was bouncing between Orlando and Ft. Lauderdale. When it went over, you got one huge dose of solar radiation. This huge dose is responsible for 1/8 of the top my head being removed with skin cancer and the multiple lesions on my face, arms, neck and any area that was exposed and...I have never been a sun bather. Sun tends to make me sick.
The Chem Trails being laid down follow the path I know the hole takes. So my guess is they are more trying to reflect the sunlight to prevent wholesale damage to the entire ecosystem than block ground radar in some two bit country. They just don't want you to know about the holes and how dangerous they are to all life. If this hole decides to take a nap over the food growing areas, it will burn the plants in the field and reduce the food production by at least a third.
Do they have other things in them? I have never know the military not to take advantage of an operation to piggy back something else on it. I have a lot of experience with the military. The scary thing about them is they tend to have the us/them mind set. This is how they condition their members to kill large numbers of people easily and without conscience. They are civilians, not people. It isn't until the soldier in the field suddenly realizes that he is nothing more than cannon fodder for higher ups that someone spills the beans on what is being done. Not only that, the basic tenet of military service is "need to know". You accept orders without question. You don't get information unless YOU need to know. The guy spraying this stuff has no idea what he is doing if in fact the planes are even manned. They can be flown via remote control and they do lay down a very perfect pattern. That is a lot harder to do than you think. My father also crop dusted for extra money.
I do know that on heavy days, I have to get in the house, shower and wash my hair and stay inside or I get sicker than a dog. I can be out running errands, suddenly feel nauseous with a headache, look up and see chem trails. I never look up and see blue skies. I try to avoid being out in the middle of the day because that is when they spray the heaviest. We have found our red van covered in brown spots that were next to impossible to wash off without detergent in a perfectly straight line paralleling 441 (State Road 7). My white van next to it was pristine without a single splash. The line continued over the shop and into Boca Raton. Periodically, I have a film on my windshield that is visible as spots at night which can only be removed by soaking the windshield in Windex, waiting 5 minutes, resoaking it and then scrubbing it off. Yes, something other than metallic residue is in those chem trails.