A and C, regarding your comment about motorsport events closing roads for safety and the possibility of doing the same for airshows, I would imagine that the problem would be where to draw the line. Air displays of course cover a very wide area compared to the much more limited "fallout zone" of a motorsport event. I grew up in Shoreham, and watched every airshow from the beach or more often from Mill Hill on the South Downs to the north of the airfield, a good distance from the paying spectators. I was frequently overflown (most memorably at low level by a Vulcan). I don't think it would be practical to close these outlying areas and all the transport links - in Shoreham this would include the coast road, the A27 and the railway. Possibly the harbour entrance too, depending on routings.