FWIW. We WAACers were at our site a few years ago, at about this time of year, & we saw a few like that.
One trail in particular, was about 15 to 20 degrees long, lasted about 15 mins, naked eye.
The air was dead calm, with a little moisture fairly high up, which made the view possible. It just seemed to 'drift' along, almost complete, with just the slightest disturbances in the trail.
We never thought, (why)?, to try with binoculars, as it was very cold n we were busy, chatting n having coffee n biccies.(Damn it was cold).
L.