AIRSPACE CLASSIFICATION in Portugal
In order to provide correct service and to specify appropriate rules airspace is classified according to the following criteria:
a. Flight Rules under which flight is permitted;
b. Separation provided;
c. ATC clearance requirements;
d. Communication requirements; and
e. Where VFR permitted the VMC minima
Due to airspace harmonization in progress throughout the ECAC members Portugal as simplified Airspace Classification as follows:

AIRSPACE CLASS "C"
(CTRs, TMAs, CTAs, Airways and above FL195)
ICAO ANNEX 11, Chapter 2.6
IFR and VFR flights are permitted, all flights are provided with an air traffic control service and IFR flights are separated from other IFR and from VFR flights. VFR flights are separated from IFR flights and receive traffic information in respect of other VFR flights.
ICAO ANNEX 2, Paragraph 4.1
Except when operating as a special VFR flight, VFR flights in Class C airspace shall be conducted so that the aircraft is flown in conditions of visibility and distance from clouds equal to or greater than:
Cloud Separation: 1 500 m horizontally | 1 000 ft vertically
Horizontal Visibility: 8 km above 10 000 ft AMSL | 5 km below 10 000 ft AMSL

AIRSPACE CLASS "G"
The rest of the Portuguese Airspace is provided with Class G, meaning an uncontrolled airspace where Flight Information Service is relayed to both IFR and VFR traffic.

For more information on Airspace Classification click here