Or you could believe that the predictive system put in by the late Philip Langsdale as part of the ATC system, actually determines how best to keep the airport moving based around the flight schedules, weather patterns and available slots.
He gave a presentation at the IET in 2012 on the optimisation of traffic schedules etc at LHR which gave some insight on how the actual air space and ground space is managed on a minute by minute basis.
Sadly, Philip died early in 2013 unexpectedly.