At night 3 white lights in a triangular shape moving slowing across the sky.At the east rim of the Grand Canyon (Yavapai Point) 11:30pm looking north northeast about 40 degrees up from the horizon on a relatively clear night I noticed one light traveling in a southern direction. A few seconds later I noticed two more lights following directly behind the first. These three lights took the form of a slightly skewed triangle. All three lights were no brighter than an average star. The size was no larger when viewing a quarter held up at arms length. These white lights were moving slowly in a straight path for about 20 seconds and then it disappeared. I beleive the lights traveled behind a cloudy area in the sky but it never reappeared afterwards where the sky was clear again.