Big deal
Grizz,
I am aware of the amount of uncertainty and workload that a non-responding crew is causing to ATC.
What I mainly attacked is the general assumption that the pilots must have been asleep. Certainly, like I stated, they could have sooner developed some suspicion that ATC was awfully quiet for a long time, but then, if you enter Serbian airspace from Bulgaria, at night you usually get a direct right to the Serbian Hungarian border, a long way to go without any other call necessary. Couple that with inadvertant turning down of the volume controls of the loudspeaker, weel, you can fill in the rest. Close to 30 minutes would be the stretch through Serbia, without any call necessary.