Unanswered ground-to-air telephone call

At 18:39:52 UTC the ground earth station placed a telephone call to 9M-MRO. The SDU acknowledged the incoming call at the avionics level — the aircraft was still a live terminal on the network — but the call was not answered in the cockpit. A second unanswered call would be placed at 23:13:58 UTC. Unanswered calls are not themselves evidence of incapacitation; they are evidence that the cabin/cockpit audio path did not complete, while the satellite terminal remained powered.