These are aerodynamic contrails. These are caused by the aerodynamic surfaces of an aircraft (eg wings) temporarily changing the properties of
the air. They are commonly seen on airliners, espeacially when landing.
This is a good example:
The points seen below the wing aren't spray nozzles but fairings containing the flap extension and retraction mechanism. They serve a double function
delaying the formation of transsonic shock waves.
They are clearly visible in this picture:
This aircraft is clearly not dumping fuel. The DC-10 has its fuel jettison nozzles located on the wings between the flaps and the outboard
When a DC-10 is dumping fuel you will get a small, continuous trail originating from those points.
This video shows something quite different:
- The trail does not originate from the fuel jettison nozzles, but frum the inner upper wing.
- The trail is not continuous
- The trail is far too large to be fuel.
The "nozzles" in post's original video are the flap hinges which are clearly visible here:
One reason the KC-10 dumps fuel from the wings instead of the boom is because the DC-10, which the KC-10 used to be, already had the system in
It is quite possible that whoever is filming is one of a few fighters who are getting "dragged" by the KC-10 across a distance too far for the
fighter to fly on its own. They sometimes fly up, below, and around the jet because after a few hours they can get pretty bored.
As to why the "chemtrails" seem to stop and then start again, take a look at this chart of relative humidity taken from
this meteorology website:
You can see from this image over Italy that as an aircraft is flying at a constant altitude, the humidity will change as it moves from one region to
another. Sometimes it will be in a humid area or a warm area, then abruptly pass into a dry/cold area. That is when you see the "on/off"
transitions. This can happen on a large scale or, in the case of the KC-10 video in the original post, a small scale.
Also, the fact that the "chemtrails" in the KC-10 video are spewing forth from every trailing edge of the aircraft, and not just the flap-hinge
nozzles, suggests that it is just regular ol' contrails.
I was searching for KC-10 videos and found this post, and wanted to clarify a few things about such a sexy aircraft.
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