airports do have limited capacity and the current Eurocontrol system apparently does not provide a provision to include this factor.
Sure, but a pilot with a brain will contact the airport directly and check there is parking - unless the airport is some ex Warszaw Pack job with 3000 sq. km of concrete 
That is standard procedure in all of aviation. At the higher end, it is automatic to call the handler. Lower down, less so, and light GA prefers to avoid handling. But if you don't make contact, there is always a risk of no parking. Or, more likely, rubbish parking on some pothole-ridden piece of grass.
I would hope that one day this functionality gets integrated into the Eurocontrol system.
That would be fun. Can you imagine airports setting up a real time apron space booking system, and employing somebody to keep the "virtual apron" updated every time there is a movement on it?
It isn't ever going to happen.
Won't stop Eurocontrol spending €100M developing the software, and generating 10000 pages of documentation for it, in their usual way
If these German airports really do employ somebody who watches the concrete and issues a REJ if there isn't the room, no wonder Greece is short of money 
Actually, if you file a flight plan via the DFS, is that really what happens? I.e. there must be a significant delay on the AFTN response message (which normally comes back within seconds, as ACK, REJ, MAN, etc) while a human checks if there is room to park. What is then the resulting message? It is really an ACK or a REJ? It has to be an ACK if OK, because in the ICAO/AFTN world you are entitled to depart the instant you have the ACK.
these German airports really do employ somebody who watches the concrete and issues a REJ if there isn't the room
It's not about parking space, it's about the capacity to handle arriving aircraft. The system is applied to scheduled flights and unscheduled flights. The airports report a certain capacity (in number of flights in a given timeframe) and slots are taken from that pool. First come first serve. The pool appears to be large, I have never heard about a slot being refused.
Actually, if you file a flight plan via the DFS, is that really what happens? I.e. there must be a significant delay on the AFTN response message (which normally comes back within seconds, as ACK, REJ, MAN, etc) while a human checks if there is room to park.
Yes, there is human intervention. They process flight plans in almost real time, simple flight plans get passed on without intervention (e.g. VFR) but if they contain the keyword REQ/ASL, they will be processed by DFS staff. It usually takes about 3 minutes.
So, no ACK for 3 minutes?
Can't say I have noticed that.
Come to think of it, most big airports must operate some system like this for airlines, because airlines are constantly up against slots, at peak times. Gatwick, Heathrow, etc. I wonder how exactly that works. OTOH scheduled flights are filing repetitive flight plans, so the airport knows what's coming.
So, no ACK for 3 minutes? Can't say I have noticed that.
Only when you file through DFS. You get an immediate confirmation that your request has been filed and then 1-3 minutes later the ACK with the slot. If you file through any other means, you have to provide the ASL/xxxxxx entry yourself.
Try filing "RMK/I AM A NAUGHTY PERSON" directly through AFTN and then try the same with DFS. I bet you get an ACK in the first case but a callback (or knock at the door) in the second. They certainly are well staffed over here.
Come to think of it, most big airports must operate some system like this for airlines, because airlines are constantly up against slots, at peak times.
The slots are allocated for the whole "season". If let's say EDDS has given out slots to 10 airliners between 1000 and 1030, then they might report something like 0-3 slots available for unscheduled IFR traffic. Mostly highly hypothetical due to plenty of capacity available but I am quite sure you would not get a slot for 0600 LOC which is when the airport opens for scheduled flights and you have 10 airliners at the holding point waiting to take off.
Regardless, now at Manchester and Berlin, I have not found the slot system too annoying. These are major airports and I accept that if you want to play there you have to fit in.
Now receiving a flt plan landing time does not match slot message from Frankfurt, when it did - that was annoying - in particular the threat of a €50,000 fine.
Achimha, thanks for the the help you provided. Today I called AIS and got the SLOT-code for the planned flight ESSV-EDDB next week. Super friendly they were!
I'll give you an update next weekend
Best regards Matthew
Matthew, just remember you have +-30mins on the slot time.
Jason, yes thanks, I'm aware of that. Use both RocketRoute and FMaster for flightplanning and very rarely my Actual Time of Arrival vary with more than a couple of minutes from ETA, excluding delays caused by i.e. ATC. ????
Best regards Matthew
ATC delays "overrule" airport slots. So, no problem.
No problem. I only mention it as when I called the people in Frankfurt about a slot they told me you must be there on time. Which of course is not correct.
