Thanks all for replies.
Originally Posted by 172driver
In theory you do not need a flightplan. In practice you do, as any flight from/to/through CAS requires one. There is not a lot of uncontrolled airspace around in Spain. Hence, you also need a radio and transponder.
What's the connection of FP requirement and radio? Do you mean I have to have a radio (to talk to tower) or I have to maintain two-way all the time? After leaving Class D - can I thank the tower and proceed without contacting departure or whoever's next?
Not that I really care for flying without talking to anyone, but seems easier that way if I want to do some "uncontrolled" sightseeing and wandering around.