The Air Navigation Order 1995

1.  General

(1) The nationality mark of the aircraft shall be the capital letter “G” in Roman character and the registration mark shall be a group of four capital letters in Roman character assigned by the Authority on the registration of the aircraft. The letters shall be without ornamentation and a hyphen shall be placed between the nationality mark and the registration mark.

(2) The nationality and registration marks shall be displayed to the best advantage, taking into consideration the constructional features of the aircraft and shall always be kept clean and visible.

(3) The letters constituting each group of marks shall be of equal height and they, and the hyphen, shall all be of the same single colour which shall clearly contrast with the background on which they appear.

(4) The nationality and registration marks shall also be inscribed on a fire-proof metal plate affixed in a prominent position:

(a) in the case of a microlight aeroplane, either in accordance with sub-paragraph (c) or on the wing;

(b) in the case of a balloon, on the basket or envelope; or

(c) in the case of any other aircraft on the fuselage or car as the case may be.

(5) The nationality and registration marks shall be painted on the aircraft or shall be affixed thereto by any other means ensuring a similar degreee of permanence in the manner specified in paragraphs 2 and 3 of this Part.