Positioning time is much like that of repositioning time or taxi time because it deals with the time it takes the aircraft to position itself from its location to the departure point of the runway. Unlike taxi or reposition times, it can have a starting point of anywhere on the airport surface as long as it is positioning it self for departure. Positioning time is essence is any time it will take a charter jet at any given point on the airport surface to get from where it is to the departure point on the runway. For instance: if a charter jet was halfway from the departure gate to the departure point on the runway then its positioning time would be how long it still has till it gets to the departure point, its repositioning time would be the point in time that the aircraft was pushed back to the departure point of the runway, and its taxi time would be the point in time that the gate was detached from the aircraft.
Positioning time can vary for a number of different reasons the most common being ATC holding delays. Due to the high volume of traffic on the ground whether being larger airliners of other charter jets priority goes to those aircraft who call ground control first and those who need it the most. Since charter jets are capable of faster and more frequent takeoffs and landings in the time it takes a larger airliner to taxi and takeoff two to three charter jets can be out of the airport. So ATC give does the best they can do with the situation but there is always going to be an aircraft holding for traffic.
Another common reason for longer positioning times are incoming traffic. Planes landing at an airport need to use the runway too so alternations have to be made between the planes on approach and the planes ready to depart. This alternation causes delays in time. The more aircraft that need to use the runway the more aircraft there will be waiting to use it. Sounds like common sense doesn’t it? Most airports catering to general aviation, charter jets, and commercial airliners will often have parallel runways. This allows for runway to be used for general aviation and charter jets and the other runway to be used for all three types of aircraft. In really big airports, there might be three or four runways being used at the same time to allow for the expeditious flow of traffic in and out of the airport.