It mentions in the article that there is not much of an application for it, but at least it least you trace the daily paths of those airliners, which in turn allows for a better understanding of -conair- ( I think that is the term used for the exhaust lines created by Air liners) pollution and how concentrated it can be in certain areas.
Trail lines from Air liners and commercial flyers have been proven to increase the presence of certain minerals and other pollutants in the air, which then translate into delivery of these minerals and pollutants to the earth below via rain if cumulus clouds form in the immediate vicinity.
Some Cirrus clouds are known to start or are aided to start as trail lines which can extend for miles and remain there for days longer than regular cirrus clouds would. Cirrus clouds act as a very thin mirror which reflects or maintains the heat that usually escapes earth through our atmosphere; and if aided by these trail lines, cirrus clouds occur at a lower elevation than they do normally.
"Not much of an application"? ...................... Right.