Boy I remember covering this in business law. I don't recall the answer
but I remember that there were several factors involved one of which I
believe was whether the owner had given up the privacy (just like
celebs give up their right to privacy by entering the public eye).
Airshow aircraft would clearly fall in that category.
However, my concern would be with the TSA. Going around taking
pictures, especially after the recent postings by some groups
concerning blownig up GA aircraftm, would generate interest.

-Robert