If we get it, fine. If we don't, usually a valid reason is stated and we do accept it. In spain, we never hear a valid reason, it is only "stand-by".
Which in itself is a reasonable position to take. But what is a valid reason ? Compliance with the Eurocontrol Flight Plan and ATFCM Adherence campaign is a valid reason to me, but is it something pilots would feel inclined to argue with the controller about ? Perhaps Spanish controllers just need to say 'Unable' ? End of story.
Well, operators also need some flexibility. We provide a service for our passengers (real people), You cannot expect us to forecast precisely (to the minute) hours in advance when an aircraft might be ready. ATC is there to help airplanes operate in a safe manner, not the other way round (e.g. airplanes are there as something for controllers to play with).
I agree up to a point. Which is why most controllers use the slot window to accomodate pilots where they can, or make alternative plans such as slot extensions , where able, to give the best service. It is certainly not a game and safety is the priority. Many controllers would be insulted if you suggested to them they are just playing some video game. However, the safety of the system cannot be guaranteed if everybody just ignores the rules and makes no attempt to comply with them.
The balance can change if that's what operators collectively want. A totally flexible system, but a less safe one, with more overloaded sectors and the chance of more incidents. The future however seems to be more based on trajectory based systems. That will require even greater degrees of accuracy than we have today, with 4D navigation required from pilots. You won't have to achieve tolerances of minutes, but probably in the order of seconds
