TK will be adding OPO/LPPR to their rather long list of international destinations.
Flight IST-OPO-IST will start in 2014, according to an interview in a portuguese newspaper by their CEO, Mr. Temel Kotil, and LIS will be getting a second daily frequency.
Source in Portuguese:
Great to see foreign companies investing in the north of Portugal!
(Also, it seems they will fly to Santiago de Compostela, Spain, next summer!)