The Southend airshow was of course over water, fantastic viewing from the cliffs area, and free to get in.
Cancelled because it cost too much. You'd have thought the income just from parking fees would have made it pay, before you get to the increase in trade, but it appears not to be the case.
Other seaside locations would most likely have the same issues, too hard to control and therefore ticket, the public access. And by their very nature, paid airshows can be watched for free by people just outside.