Unidentified aircraft encounters
Question for the Network -- If you encounter an unidentified aircraft flying in commercial airspace with its transponders off, what do you do?
Reason for asking -- I am a former aviation professional now working as an adjunct professor at a snotty Ivy League school (in New Haven, if you must know...). I am writing a research paper on (thus far, hypothetical) covert efforts to engineer the climate and whether the world at large could detect them. Such climate engineering would be implemented by as yet non-existent high altitude crop dusters -- 737-sized aircraft flying up through commercial airspace on their way to the lower stratosphere. If they wanted to operate covertly, they would fly with transponders off without interact with ATC (I know this sounds crazy, but bear with me...). The question is -- if you were cruising over international waters at FL 360 or whatever and encountered such a bird, besides avoiding it, what would you do? Would you report it to your ops control center? Or somehow warn other aircraft in the area? Would you report it to any national authority? Or to ICAO? Or post something about it on this network? Is there some SOP that dictates your response, or would you simply avoid it and fly on? What I am really after is -- if lots of pilots had such encounters, would the world somehow be put on notice about such aircraft, or might it remain a secret?