Mackeral sky and the breaking up of a contrail

Here is a mackeral. Look at the stripes on its side. No wonder mackeral sky gets its name.

Look at the aeroplane vapour trail above Harter Fell at Mardale.

Some time later the trail had broken up. It broke up into mackeral sky. A lateral wind has spread the trail sideways thickening the trail but it has banded along its line. I will need to see if this is frequent.