Didn't see it myself as I'm over in Warwickshire so a bit far out, but I've been following the Phoenix area reports for a while now and this is the third or fourth mention of a triangular craft in that region in the last couple of months.
Quick question for those who did witness it - was the triangle shape solid or were you just inferring the shape from three separate light points? I always wonder about this with these reports because the distinction matters quite a lot when you're trying to work out whether it's a single craft or formation flying. Also roughly how large did it appear relative to, say, a full moon held at arm's length? That's a rough but useful way to gauge apparent size without equipment.
I ask because the crop circle community sometimes cross-references UAP sightings in areas where formations appear shortly after, and there's been some documented overlap historically. Not saying thats what this is, just curious whether anyone on the ground got a proper look at the overall shape as one continuous object.