On 3 Nov, 13:57, Les Crossan
wrote:

May be a distrail but more likely that something other than an aircraft
has caused that part of the cloud to glaciate and once the process has
started the ice will propogate through the cloud sheet?? So not
evaporation but glaciation / virga (what used to be called fallout).

Looks a bit high for stratocumulus (pic1)

Hi, Les,
Make that Ac (!)
Apparently it's a fallstreak

http://en.wikipedia.org/wiki/Fallstreak_holes

Ken
Copley