CLOSE UP of United Airlines releasing "Chemtrails" over Brisbane using Nikon P900 Camera.

This video probably raises more questions than it answers.
Lots to consider here:
Trail is not visible until aligned with the tail and no clear evidence of being released from a nozzle. Possible explanations:
1. Trail is actually a "contrail" and nothing sinister happening here.
2. Particulates are released from nozzle but don't "materialize/visualize" immediately. Any scientific explanation of this???
3. Particulates are released in the exhaust of the engine.
4. Particulates are mixed with the fuel. As trails typically have a distinct beginning and end, this would likely be injected from a separate tank at a set time possible activated by GPS mediated switch.