Hi there! I would say it's a Ferienflug if it's all about getting from A to B (e.g. Stuttgart - Paris; Munich - Tenerife) at a cheaper price. These flights are generally organized by a tour operator. I'm not sure though what the difference would be from a charter flight. Or is this just a new name for a charter flight??? Does anyone know??
If it's a flight in a helicopter or airplane, e.g. over the cliffs of Dover to see the view, then you would call it a Freizeitflug. But this term - as far as I know - is used by organizers of such flights. I'm not sure your common Joe would use that word.