Triangle shaped craft flying at high altitude and speed.It was flying Northwest to Southwest. It looked like it was flying from the Mountain Home AFB to Utah at first. It flew quite slow and High in the air then it appeared to turn North and towards space. The lights dimmed as it flew off and it was gone in the blink of an eye. From my vantage point he was flying through the Big Dipper in the sky and turned near the North Star. I've never seen anything like this before. It was not any kind of aircraft since they couldn't turn and fly higher that quickly nor would they turn off their lights in our airspace. We live a mile from an airport.