a) Aircraft shall not be flown closer than 500ft to any person, vessel, vehicle or structure.
b) An aircraft should not fly over a congested area of a city town or settlement below a ruleheight of 1,000ft above the highest fixed obstacle within a horizontal radius of 600m, or be able to glide clear, whichever is higher.
c) An aircraft shall not fly over an organised open-air assembly of more than 1000 persons below 1,000ft or be able to glide clear, whichever is higher
Air Navigation Order Section 2: The Rules of the Air Regulations – Section 3 – Rule 5
Landing and taking off gives exemption from the low flying prohibitions.
