Funny the German weatherman called it a 'snake', wasn't there a certain 'snake airlines' character who is accused of shillery quite often here on this subject..
I guess 'this guy'(!) is saying that as jet engines have been increasing in efficiency these 'snakes' have become more apparent; I certainly don't remember these skies in my youth. Every sunrise and sunset I see grids, increasing in frequency always near to position of the sun on the horizon. Not pretty .
Anyway, one can't prove a negative; also I could just say that these scientific facts would be the perfect cover for the spraying of geoengineering chemicals/ virus or whatever !
As ever here, going out from the same door through which I entered !