43.—(1) Where it appears to the CAA that two or more airports are airports serving the same area and either—
(a)that they are managed by the same airport operator; or
(b)that they are owned by the same person, or by members of the same group of companies, and they operate as a group of airports whose activities are co-ordinated by the airport operators concerned,
any conditions imposed or modified by the CAA in pursuance of Article 31(3) or (4) in relation to any one of those airports may be framed so as to prescribe a limit or limits operating by reference to the aggregate of amounts levied by way of airport charges at that airport and amounts so levied at the other airport or airports.
(2) For the purposes of paragraph (1) a body corporate and each of its subsidiaries shall be treated as members of a group of companies.
(3) In paragraph (1) the reference to airports serving the same area is a reference to airports in the case of which a substantial number of the passengers departing from, or arriving at, the airports by air (other than those interrupting their flights there or transferring from one flight to another) have as their original points of departure, or (as the case may be) as their ultimate destinations, places situated within the same area.