Re: HZ posters could figure this out.
Many aircraft, both military and civilian, fly polar great circle routes north and south, even if there are no nearby airports in those directions. Modern aircraft have a tremendous range, and the airport of destination could be thousands of miles away. Not knowing where you live, I can't be precise about this.
Contrails do indeed encourage cloud formation under the right conditions, but this is a natural and unintentional phenomenon with the "seeding" being done by the water droplets, ice crystals (and possibly soot) in the contrail, not by any deliberate "seeding" procedure on the part of the aircraft.