I actually think that Mosquito Control intentionally flies low for the sole purpose of getting that oily substance in the water for larvacidal control of mosquitos. It's much easier to kill them while in one area (larva in water) than after they grow wings and diffuse over an area.
I worked for EVMCD
http://www.volusia.org/mosquito/ for a few years and went on several outtings a week in a chopper. Most missions were larvacidal and targeted larvae developing in rainwater/hi tide water - accumulated in marshes. It was a semi-failure if spraying for adults had to be done.
Anyway........ sounds like a misunderstanding on the helicopter pilot's side. I don't remember reading anywhere about a commercial plane getting close, Erick.
Although the CRAZIEST thing I ever saw was a MacDill jet miss Bayflite's kite by no more than 50 feet out by the Undertow. Wish I had that sh.it on film... it was insane. Plane was going Mach something. Didn't even hear him til he was 100 yards past us. He literally missed BF's kite by 50 feet (max).
Raul saw it too, I think.