I'm 50-something years old, and I remember a time, 20 years ago or so, when vapor trails dissipated within a few seconds. They ALWAYS dissipated within a few seconds. The contrails NEVER crossed the sky from horizon to horizon, and they NEVER spread out to become a hazy cover.
I'm sick of these hacks who pretend to be "experts", denying these persistent aerial vapor trails. They are either complicit or ignorant; no other explanation! Ptoooey!