For AOC holders ("air transport undertaking") it gets even more interesting. Art 130 (2) states:
"(2) Subject to the provisions of this article, an aircraft in flight shall for the purposes of
this Order be deemed to fly for the purposes of public transport:
(a) if valuable consideration is given or promised for the carriage of passengers or
cargo in the aircraft on that flight;
(b) if any passengers or cargo are carried gratuitously in the aircraft on that flight by
an air transport undertaking, not being persons in the employment of the
undertaking........."
So - if you are an AOC holder any flight you do carrying non-employees is a PT flight whether or not they are paying passengers.