Doubler, schmubler.
1. I am judging speed past the little thin cloud.
2. Assuming the “airplane” was at 30,000 ft, the “contrail” would be visible for over 200 miles.
3. Assuming 600MPH, the “contrail” be visible for 20 minutes
4. If the disturbed part of the “contrail” had been blown apart by the upper winds for 20 minutes, it would have dissipated much more.
5. An aircraft transiting LA at FL30, or more, is not going to descend to a low enough altitude to stop producing a “contrail.”
6. The only characteristic this item shares with “contrails” is that it is long, and sort of cloud shaped.
DG
You need some more info about contrails. The article is aimed at “chemtrail” people, but the contrail info in the links is very informative.
http://www.tetrahedron.org/articles/health_risks/Contrail_Controversy.html
Contrails can persist for 10 hours or more, depending upon temperature and humidity. Those can change even when a plane is at a constant altitude.
Search on “contrail persistence.” Do image searches on “contrails” and “wide contrails.”
The theory is not that UPS902 descended enough to cease creating a contrail, but that it passed from cold moist air over the Pacific to drier warmer air (changing the dew point) as it approached land.