And for that occasion I go to a field and it happens to be that there is nobody I can call the Brussels ARO myself to close it right?
Close it from the air, it is the most convenient way.
And to fly international from one shengen country to another I don`t have to land at a customs field?
For flight whithin Shengen countries thre is no need to land at customs field, only for the first time, you do the ENTRY to Shengen area.