Empty Legs

Booking an empty leg is a much cheaper alternative than booking a regular charter flight, these flights are available at short notice
and are flexible in the sense that they can be organised for a drop off en route to their re-positioning location.

Empty leg can carry the risk of being unreliable, for example: if the subsequent flight is cancelled or rescheduled then that aircraft
may not need to be in a different location and therefore that could affect your empty leg flight.