Tactical Decision
Occassionally an airway sector can experience a short duration burst of traffic which may result in a request to an airfield to hold a couple of departures for a few minutes. The request may be with little warning and is not the fault of the airfield. There may be an ultimate benefit to the traffic concerned, instead of level capping at an uneconomic cruising level, a gap of 2 or 3 minutes may be all that is required to ensure a better en-route profile......additionally there may be other reasons which are not readily transparent to either the airfield or the traffic on the ground. In the instance you report it is quite possible that the airway sector had agreed not to impose flow at all, to the benefit of the overall traffic situation....in other words agreeing to short duration overloads to keep delays to a minimum....but reserving the right to impose short-term tactical measures as and when necessary in the interest of safety and service provision.