To avoid problems associated with last-minute slots when departing on Z flightplans, I always try to get my IFR clearance while still on the ground. Either through the aerodrome radio operator or via mobile phone.
How do you get an IFR clearance via phone in Germany?
How do you get an IFR clearance via phone in Germany?
The same way the radio operator of the airfields do: By calling the control centre in charge. I have no idea where the phone numbers are published, the few I ever needed I got from airfield staff.
