Bit of an odd one to ask here since I'm based in Staffordshire so obviously I wasn't there, but I've got a mate who was visiting family in Arizona last week and he sent me a video on Thursday night that shows what looks like three lights in a slow triangular formation. He had no idea what he was looking at and sent it to me because he knows I follow this stuff.
Is this the same thing people in this thread are talking about? I want to make sure before I post the video properly. The lights in his clip seem pretty steady, not blinking like aircraft nav lights would, and the whole formation holds its shape for at least a minute before it drifts out of frame. He filmed it on his mobile around 9-9:30pm local time if that helps narrow it down.