In article ,
Nathan Young wrote:

On 07 Dec 2005 00:36:05 GMT, Blanche wrote:

An advertisement for Sci-Fi Channel's new mini-series?

Well, this did happen in the Minneapolis area, so perhaps it had
something to do with the light pillars mentioned a day ago. :-)

I could throw in some more than usually uninformed speculation (even for
this group . . . ) about a random dot of frost forming, causing the
airflow to spread out laterally just a bit; gases cool when they expand
(happens in nozzles and many types of refrigerators); result is more
frost forming in the region just behind the dot; and the
forward-pointing triangle grows toward the rear of the plane.

Fits the available data presented thus far, and stranger things happen
in gas and liquid flows all the time -- but I have no idea if anything
like this is really happening here.