Here yar Andy, I took this photo of a black line last year. It's not the clearest pic but it's good enough.
The plane is alongside the black dot. Note that the line extends forward of the plane, to the horizon.
.

yes, but andy, that pic doesnt have the pulsing

On a fractionally more serious note.

Surely any number of interference pattern causes could bring about changes to the contrail. Temperature variations, wind fluctuations, sonic resonance could all create currents.

btw I am not contesting the claim that they are spraying chemtrails.
As already mooted though, it's solid empirical, peer appraised, evidence that's required there.

EDIT: I don't want ppl thinking I'm saying chemtrails don't exist btw, they definitely do exist. Simply that there are obviously different types of trails and how best to identify them.

Hmm well it could be useful to exclude commercial flights perhaps?
As I'm willing to bet the planes concerned are ofc not commercial flights

another question, with the same premise, what causes the black 'parallel' lines that are rare but not unseen by myself and many others?

What 'chem(s)' are being dumped?
What evidence is available?
Is there a known range of chems and a distribution map of what/where?

Operation Popeye (Project Popeye/Motorpool/Intermediary-Compatriot) was a US military cloud seeding operation (running from March 20, 1967 until July 5, 1972) during the Vietnam war to extend the monsoon season over Laos, specifically areas of the Ho Chi Minh Trail. The operation seeded clouds with silver iodide, resulting in the targeted areas seeing an extension of the monsoon period an average of 30 to 45 days. As the continuous rainfall slowed down the truck traffic, it was considered relatively successful.[1] The 54th Weather Reconnaissance Squadron carried out the operation to "make mud, not war." [2]
The resultant rain and subsequent flooding of the nearby Song Con River is sometimes blamed for the move of POWs from the prison camp at Son Tay and therefore, the failure of Operation Ivory Coast.[3]

In Britain, it has been alleged that before the devastating Lynmouth floods in Devon in 1952, the RAF had been conducting secret rain-making tests. Aircraft showered clouds with silver iodide, on which water droplets formed, became heavy and eventually fell to the ground as rain. In the next 12 hours nine inches of rain fell – 250 times the normal amount for August – and 35 people were killed.

Former North Devon MP Tony Speller, then a 22-year-old soldier who helped in the relief effort, sought answers from the MoD.

“I have no doubt they were seeding in the area because there were RAF log books to prove it, ” he says now. “Of course the MoD denied any knowledge but that is not to say it did not happen.”

Speller, now 76, adds: “I doubt we will ever know the truth.”

What started nearly 100 years ago with the earliest cloud seeding experiments has developed into a wide range of technologies as different eras have presented different challenges. The last few Mud Reports have concentrated on global warming, regardless of its causes, as the main driver of our current era's extreme weather events. Understanding this full well, research by the military and corporations has concentrated on 'getting ahead of curve'. Consequently Solar Radiation Management [SRM], Stratospheric Aerosols, Geo-Engineering, Climate Engineering have all evolved as offshoots of cloud seeding research and development throughout the decades.

In 1990 the idea of spraying aluminum oxide from jet aircraft was patented by Hughes Aircraft. The plan proposed to seed the metallic particles was to add the tiny particles to the fuel of jet airliners, so that the particles would be emitted from the jet engine exhaust while the airliner was at its cruising altitude.
SUMMARY OF THE INVENTION: Patent #5003186
A method is disclosed for reducing atmospheric warming due to the greenhouse effect resulting from a greenhouse gases layer. The method comprises the step of seeding the greenhouse gas layer with a quantity of tiny particles of materials characterized by wavelength-dependent emissivity or reflectivity, in that said materials have high emissivities in the visible and far infrared wavelength regions and low emissivity in the near infrared wavelength region. Such materials can include the class of materials known as Welsbach materials. The oxides of metal, e.g., aluminum oxide, are also suitable for the purpose. The greenhouse gases layer typically extends between about seven and thirteen kilometers above the earth's surface. The seeding of the stratosphere occurs within this layer. The particles suspended in the stratosphere as a result of the seeding provide a mechanism for converting the blackbody radiation emitted by the earth at near infrared wavelengths into radiation in the visible and far infrared wavelength so that this heat energy may be reradiated out into space, thereby reducing the global warming due to the greenhouse effect."

Most of those questions are answered in the documentary What in the World are they spraying, which I'm sure you must have watched, no?

I don't think anyone here has actually given it much thought beyond whats already shown in conspiracy media angel.

I think they have.
For example, did you know that most chemicals in aerosol format are invisible? Why for that matter should we associate visible plane trails with chemical dispersant?

Yes I do, hence the reason why they put stuff IN some aerosols so you know WHERE your spraying.... Get it?

Chemical shelling for example is often completely undetectable except by special equipment.

You're also making assumptions about me being argumentative
Nope...you're doing it again, avoiding answering a perfectly polite and reasonable question I asked based on what you wrote

The main difference that can be seen with the eye is the way the stuff that is visible reacts. Contrails seem to dissipate quite quickly depending on the weather/temp. Even if they stick around for a while, they usually just hang where they are and then disappear.

People are noticing that these trails, whatever they may be, are behaving quite differently in that they just don't appear to dissipate at all and sit there indefinitely. I've seen it myself where they start out fairly ordinary looking but just stay there and start to spread, particularly when you see the criss-crossing others have mentioned.

Eventually, they all weave together to form a blanket.

Thinking about it a bit more, it does lend credence to the weather manipulation theory or perhaps for some reason best known to 'themselves', shielding the earth from solar effects?