An A321, en route from Antalya to DUB was out of communications for FORTY minutes over central Europe yesterday (from Prague to the Netherlands) and communications were only restored when the Dutch AF sent up two F-16s to ask them if they wouldn't mind getting back in touch.
It's hard to believe that any crew can fly over busy European airspace for forty minutes and not notice a lack of communication!
Incident: Onur Air A321 from Prague to Netherlands on Jun 20th 2010, loss of communication for 40 minutes