I'm trying to think of some good excuse for the pilot or flight attendants not to tell the passengers but I can't think of one. Neither can other frequent flyer friends I have spoken with. The situation sounds like it might be similar to that cruise ship mishap the other day. One news report says apparently the ship's crew did not notify the Coast Guard. A passenger did that!
"I'm trying to think of some good excuse for the pilot or flight attendants not to tell the passengers but I can't think of one."
You are not a pilot from that statement.
There would be no reason to tell the passangers since every plane in the system at the moment of outage has clearence to a destination and no more traffic is allowed into the airspace.
Even if sll communicstion is lost until every plane in on the ground there is still no danger.
Even the airfield is clear for each landing in the specified time slot.