Licenced aerodromes are required to keep a record of movements (T.O. and landings) and these records are audited by the CAA. Dependant on the number of movements and the complexity of them the CAA may require a minimum level of service: A/G, FIS or ATC etc. A civil licenced aerodrome (i.e. airports) must be available to all and on equal terms and this is subject to audit. A private licenced aerodrome is not required to be open to all and may if it wishes have its own conditions of use, and as it sees fit (PPR etc), including booking in and out. It is particularly important to have a pilot booking in/out system where there is not a dedicated radio operator as may be in the case of a/g. The police may apply pressure on the owner when they wish to exploit the informal customs/immigration procedures. This is particularly true for movements subject to the anti terrorism act: to and from the I.O.M., Channel Islands, Eire and N. Ireland. The aerodrome may of course be limited (licenced or not) to a maximum number of movements at different times, subject to its planning permission. I don't know of any aerodromes that are required to have a booking in/out system subject only to a planning requirement but they may exist.
So there is a wide range of reasons for booking in and out.
Last edited by Fl1ingfrog; 22nd Jan 2020 at 10:39.