Morocco
My understanding is that members of an ICAO State do not need overflight permits.
We are a non schedule Public Transport company and we never ask for permission for O/F. We have never been asked for a clearance number and never had any problems.
This is unlike Tunisia where it is clearly stated that ICAO members only need to file a flight plan but we are always asked for our O/F permit. That said getting an O/F permit is always very quick (30 mins)
What have others found?