at the time the ticket is issued or, if it is altered, at the time it is last altered, he would not (assuming there is no change of circumstances) be a chargeable passenger in relation to any flight in the course of his journey, and

by reason only of a change of circumstances not attributable to any act or default of his, he arrives at or departs from an airport in the course of that journey on a flight the prescribed particulars of which were not shown on his ticket at that time,

at the time the ticket is issued or, if it is altered, at the time it is last altered, he would (assuming there is no change of circumstances) be a chargeable passenger in relation to one or more flights (“the proposed chargeable flights”) in the course of his journey,

by reason only of a change of circumstances not attributable to any act or default of his, he arrives at or departs from an airport in the course of that journey on a flight the prescribed particulars of which were not shown on his ticket at that time, and

but for this subsection he would by reason of the change be a chargeable passenger in relation to a number of flights exceeding the number of the proposed chargeable flights,

at the time a passenger’s flight begins, by virtue of section 31(4A) above he would not (assuming there is no change of circumstances) be a chargeable passenger in relation to the flight, and

by reason only of a change of circumstances not attributable to any act or default of his, the flight does not return to the airport from which it departed or exceeds 60 minutes in duration (excluding any period during which the aircraft’s doors are open for boarding or disembarkation),