What are empty leg flights?

 An empty-leg charter flight is where an aircraft is required to position to a particular airport for a one-way charter or return to its base empty. Private business jets often fly empty if their clients only fly one way and the jet has to return. An average person can fly on one of these “empty leg” ferry flights at a large discount.

The important criteria here is that you’d need to be flexible with your travel plans due to the nature of empty legs. Generally, it is a matter of weighing up the cost advantage versus such constraints.