I know that the subject of this discussion is taking passengers on training flights, but please allow me to make a slight tangent.
I understood that the requirements of a private flight was that the pilot did not receive personal gain, i.e. no profit margin. I am a little confused. Does the cost of the aircraft now constitute 'personal gain'?
As an example; a recently qualified PPL wants to show off his/her new skills to his family. Dad, recognising that son/daughter is probably skint from financing the training offers to cover the cost of the aircraft for the "show-off flight". Does that then constitute a commercial flight?
Before I get bombarded, I am in the early stages of my PPL training, so this is purely hypothetical.