I went to Silverstone a couple of weeks ago for the Historic GP races which were excellent. However the point is members of the Vintage Aero Club were there and took off towards Club Corner while the racing was still on directly over the crowds in the enclosure. So obviously different rules apply at different circuits. I remember the racing being stopped at Snetterton to allow a Cherokee 6 to land on the Revett Straight, presumably to let a driver in. Lack of consistency somewhere.