An interesting point about image copyright comes up with certain buildings.
For example the Gherkin and London Eye both are under copyright, and theoretically you cannot sell an image containing the design of the structures without obtaining permission. How easy this is to enforce I don't know........
Essentially though any image you take with your camera from public place is your image. And when it comes to 'selling' images be very clear what you are selling, a print is one thing. As soon as someone talks about *using* an image for any purpose other than their own personal enjoyment then you are looking at licensing the use of that image. For that you need to discuss what medium the image will be used in, for what duration, and for what number of reproductions.
Have a look at the freelance website for some of the discussions around this issue:
http://www.londonfreelance.org/feesguide/photo.htmlA final point is that any images taken on private property *at an aisrhow* usually are excluded from use commercially in the terms of the ticket sale. It's an exclusion on the ticket terms and conditions preventing professional photographers selling images from the airshow without permission. Again theoretically they could chase you down for breaching the terms of your access to private property to take and then sell the images....not very likely but something to bear in mind.
Steve