The fellows in this video have been tracking commercial planes over Australia, and one particular flight, Qantas QF63 was tracked from Sydney to Johannesburg on two different occasions as it passed over Hobart, Tasmania. The tracker, 'Youtuber' peekay22 was able to use the flight tracker to twice predict the plane's arrival over Hobart and called Tasmania where another person made visual ID of the plane as it was observed to pass overhead. He also confirmed the planes red tail color as it passed overhead. On the first occasion, the plane left a non-persistent contrail, but the second day it left a persistent horizon to horizon "chemtrail". So, they basically debunked the claim that ordinary commercial flights don't make persistent contrails, though they continued to call the latter case "sparaying". The first case, to their minds, was just a case of the plane "not spraying". They also seemed outraged that the plane did not fly a straight path between the two destinations. Chemtrails sites never explain aviation, but for anyone interested, here is a link to a "Great Circle" mapping utility, I have put in the route here. A great circle, or geodesic, path isn't a joke, it is actually the shortest route between two points on the surface of a sphere. Variations in fligt paths are not unusual. Using either radar, turbulence or wind speed forecasts or reports, pilots plot their courses to avoid storms, high headwinds, or turbulent conditions. They may also gain considerable speed if they are able to change course to run with high speed rivers of air called jet streams. Here are some examples of actual passenger reports from other days of the same flight Qantas QF63.