I would guess that the contrails predated the Trolloc Wars; and probably also the Breaking.

They were being left by something moving across the sky. And whatever left the wide and long burned patches was clearly post-Trolloc Wars.

Something was going on.

Contrails being left behind by aircraft or missiles, maybe even satellites or space debris entering orbit though they seemed to be aircraft or missile contrails.  The wide and long burn marks on the land itself could indicate laser weaponry or nukes which would support aircraft or missiles, as if left over from the Age of Legends or an age before.  There were references to Mosk and Merk (Moscow and America) and Glem/Glen riding in the belly of a lance of fire (Glen Armstrong and the Apollo Missions iirc.  This ties in the Anla the wise counselor who is Ann Landers and other bastardizations of things from our current time which RJ loved to use to indicate the changes that occur with oral histories handed down through many generations.)

 

The Trollocs seemed to have had an early and complete victory over the forces of light to which the land itself seemed glad for a weapon to have been made.  There was the Trolloc monument in place of the monument to Artur Hawkwing celebrating his victory over the shadow's forces in the Trolloc Wars which indicated that either in the AOL or the Trolloc Wars the Trollocs won out, and then turned on each other for food.  We saw only Grolm in this world and the Seanchan forces used these animals like the Grolm and Torm and Lopar from these mirror worlds to defeat their smaller Blight and shadow forces right after the breaking.  Lanfear might have been bringing these in from yet another world as they seemed to appear as she willed to force Rand into running for the pillar stone and to force him into taking them back to the main world to which all others were the reflection.  She could have used gateways though at a distance, or have brought them in and staged them, maybe binding them with air and then releasing the weave to set the different bands of Grolm on the hunt.  Lanfear seemed to have greatly underestimated Rand's bow skill.  

Obviously they were contrails, but from whom?

The Trollocs clearly won, but they don't seem the sort to develop aircraft. Did the forces of Light rally and start developing technology which they used to burn the shadow from the land? Or did human living under the Shadow's thumb advance technology in a Dark Age?

I don't know why, but for some reason that was always one of the most interesting parts of the WoT for me.

I have a strong suspicion that during the early books Jordan had intended to expand on that. Just because of how much work he put into thinking of the background of the world he wrote in.

Like it says on the tin.

The streak in the sky could be a rocket or a plane's contrail. In the AOL it is known (and Lanfear admits it) that humans even visited other worlds. It might be a satellite or an unmanned drone, or a capsule froma space station with half a dozen skeletons in it finally making orbit. For a land glad to have a weapon made, it was certain that the shadow had been the victors of the Trolloc wars.

I don't think it would be a space relic from the AoL(or earlier), nobody ever mentioned seeing such things in Rand's world.

Also, I had the impression that the streak in the sky was somehow, at least tangentially, related to the burned swaths.

Unmanned drone is an interesting idea.

There is more than one way to win a game of Sha'rah, and Ishamael/Moridin was once grousing about making a terrible mess of an attempt at brute forcing it. I always took that as an allusion to the Trolloc Wars.

And, IIRC, in the mirror world in question it appeared the Shadow had won the Trolloc Wars, and that world was in a dark age. Am I remembering correctly?

So, perhaps there really is a nation in the blight and in that world the Blightlanders recovered or developed some technology and used it to scour the world, or at least the north, free of life.

Alternatively, maybe Ishamael's attempts at knackering social cohesion didn't work as well and the Randlanders got their acts together logn enough to develop some tech which they used to salt over the Blight and, to be sure, scour the land for a good ways south.

But, considering how the land was glad to have Loial make a weapon I am more fo the opinion that the Shadow had some success.

Either way, I could see it being a jet and that fitting perfectly fine in the story.