I think the idea of chemtrails is rediculous. As a pilot I know that Turbine aircraft ommit contrails and some even dump water because it provides
more power durring combustion (ironicly).
The airspace around NYC is very busy and would not alow for such activity. The Class B airspace from LaGuardia(KJGA), KJFK, and Newark(KEWR) combine
and have various controling groups, NY approach, LGA approach Tower&Ground, JFK approach, Tower&ground, and Newark approach, Tower and Ground. In
class B airspace it is Against FAA regualtions to fly without a Mode C transponder(with altitude encoding capability) whithin 30 miles of the class b
airport(just for refference most aircraft have one, even little Cessna 152s). A transponder is a beacon which ATC can track your aircraft with.
Military aircraft are controlled by this as well. Furthurmore any aircraft flying above a certain altitude (not sure what it is I'll probably Edit it
in later) have to fly IFR, IFR aircraft have to remain under NY approach's control. In NYC it would be easy for an aircraft to wander into some
one's airspace if they were not conducting themselves properly with ATC. If they did ATC would get pissed off.
Mabye chemtrails are possible but deffinately not in NY-class B airspace.....which covers all of NYC.
See NYC Sectional:
skyvector.com...-15-3-2625-3046