'Ghost Flights' are in my understanding the same as crewmeal sugests.
There was an article in the papers just before the bmi and bmed merger of ghost flights being operated by bmed from Cardiff-Heathrow and back daily in order to meet the target set by Heathrow for operating slots.
What is being described here is positioning legs of flights to get the aircraft from where it is to where it's needed. Obviously Thomas Cook sends their aircraft around the UK to meet demand. I'm sure that some of these sectors maybe utilised better by operating on a 'W' pattern to increase demand.