Good, relevant comments above. When there are airfield delays the CTOTs are taken into account, and it is usually the unrestricted aircraft who suffer the longest airfield delays, simply because of the difficulty of negotiating another CTOT and the possibility of long en route delays as a result. If there are a lot of aircraft in the system already, then unfortunately aircraft with CTOTs that in the pilot's opinion can be easily met, have also got to be subjected to the airfield delay. The OVERALL flow rate is still maximised. At times of runway alternation, start ups also have to be regulated to ease the workload on GMC - opposite direction routeings, choice of departure runway as 1500 approaches, involving close co-ordination with Air Departures, etc.