simon
while clearing all altitudes for NORDO (no radio) plane with an expected altitude change will cause havoc, it will not cause a collision...controllers will have to do more work, pilots and planes will have to use more fuel, people will be delayed, but they will not die.
I do THINK, SPECULATE, conjecture, that the LEGACY crew may have turned down their radio volume in one of a number of ways in order to chat up the guests in back as they came to the cockpit to look around. It happens.
And for the legacy crew to NOT hear a radio transmission would make me suspicious as a pilot and I would key the MIC and ask for a radio check.
1 hour of flying is more than 400 nautical miles...that is a long way to go without a how do you do?
j