Where do y’all get this stuff. Whether it’s a B 17 at higher altitudes or a commercial airliner, it is condensation from the exhaust , the moisture in the exhaust cooling rapidly along with the combustion air returning to atmospheric pressure which at 35,000 ft is low , causes the visible moisture. Depending on the humidity at the altitude, temp, and the winds aloft, determines the shape, and duration. I’ve passed aircraft where the contrail disappears quickly, and other times can last for minutes. Wing tip vortices ( basically a horizontal,mini tornado) can also affect the shape....Doesn’t matter what the fuel or what’s in it,we use mil spec fuel in commercial aircraft, gasoline in WW II.... It’s the moisture, that’s it....maybe the burned additives that have endured temps of 1500c might contribute something, but I doubt it....
Wing tip condensation/ contrails mainly occur during high lift/ drag configurations of the aircraft, mainly rotation at takeoff and flaring for landing. Extension of the wing air brake ( spoiler) can cause condensation. And upon touchdown as the ground spoilers deploy, condensation can sometimes be seen for a few seconds. But, this only happens on high humidity days such asfog, mist, rain ,etc...Wing tip condensation,at high altitudes with substantially lower humidity than the surface and low drag , high speed configuration does not normally occur....
Watch this video, the center one. You’ll see 4 contrails ,each from the 4 B17 engines and there is a segment showing two P 38’s pulling two contrails each.....
....have a nice day...
