An airplane is not a public area, neither is the post TSA checkpoint. Public area is something that was designed and built using taxes. An airplane is a private area and if anything, the airline can demand you stop taking pictures. Or the gentleman you took the picture of can eventually call the cops on you for acting suspiciously on an airplane and taking illegal pictures.
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An airplane is not public space. Since when did airplanes become public spaces?
You keep using that word. I do not think it means what you think it means.