An American Airlines Boeing 777-200, registration N787AL performing flight AA-63 from Paris Charles de Gaulle (France) to Miami,FL (USA), was enroute at FL340 over the Bay of Biscay about 240nm north of Santiao de Compostela,SP (Spain) when the crew reported smoke in the cabin and diverted to Santiago de Compostela for a safe landing about 45 minutes later. The occurrence aircraft is still on the ground in Santiago de Compostela about 4 hours after landing.