Also happens at high humidity. I've seen vortex trails off the rear wings of race cars, which generally run at a fairly low altitude :-)
> Except that this plane is showing contrails...generally denotes high > altitude. > Norm > > Bob W wrote: > > > <snip>In the late autumn at about 5.30/6pm the moon was generally very > > low in the sky > > > >and planes were coming in once a minute exactly as you see in that photo. > ><snip> > > > > >
