That's interesting Fiverings! I can't of anything of ours that would only show one red light either and I can't find anything on the net! I'd think there would've been noise from jets, even from that distance! Did you hear anything? Is there any possibility they could have been the dreaded Chinese lanterns?.....Though the fact they were flying in formation would suggest not!
No, I was outside but there was no noise. They were moving steadily but not fast, my most rational thought was helicopters on some sort of night exercise, but lights didn't tally, and why a formation of 6?