It is more strange when you see the plane spaying and then, suddenly stopping while continuing its cruise. Somebody might ask, if that is really CON-trails, what change so suddenly in the environment condition that suddenly disappeared? Nothing because he flied at same altitude (he cannot change in a second hos altitude in order the temperature to variate so much, etc). So if the plain didn't stop its engines because he continued to move forward, then the only explanation is that these were not normal contrails! Has nothing to do with the plane propulsion system.

Then, if those are not related with plane propulsion, means that they are something different, that this a separate system altogether, put there with a purpose...

From here we can be opened to anything...